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Message-Id: <200703170055.09700.kernel@kolivas.org>
Date: Sat, 17 Mar 2007 00:55:09 +1100
From: Con Kolivas <kernel@...ivas.org>
To: linux kernel mailing list <linux-kernel@...r.kernel.org>,
ck list <ck@....kolivas.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Ingo Molnar <mingo@...e.hu>
Subject: [PATCH][RSDL-mm 5/6] sched: implement rsdl cpu scheduler
From: Con Kolivas <kernel@...ivas.org>
Rotating Staircase Deadline cpu scheduler policy
================================================
Design summary
==============
A novel design which incorporates a foreground-background descending priority
system (the staircase) with runqueue managed minor and major epochs (rotation
and deadline).
Features
========
A starvation free, strict fairness O(1) scalable design with interactivity
as good as the above restrictions can provide. There is no interactivity
estimator, no sleep/run measurements and only simple fixed accounting.
The design has strict enough a design and accounting that task behaviour
can be modelled and maximum scheduling latencies can be predicted by
the virtual deadline mechanism that manages runqueues. The prime concern
in this design is to maintain fairness at all costs determined by nice level,
yet to maintain as good interactivity as can be allowed within the
constraints of strict fairness.
Design description
==================
RSDL works off the principle of providing each task a quota of runtime that it
is allowed to run at a number of priority levels determined by its static
priority (ie. its nice level). When each task is queued, the cpu that it is
queued onto also keeps a record of that quota. If the task uses up its quota it
has its priority decremented to the next level. Also, if the cpu notices a quota
full has been used for that priority level, it pushes everything remaining at
that priority level to the next lowest priority level. Once every runtime quota
has been consumed of every priority level, a task is queued on the "expired"
array. When no other tasks exist with quota, the expired array is activated and
fresh quotas are handed out. This is all done in O(1).
Design details
==============
Each cpu has its own runqueue which micromanages its own epochs, and each
task keeps a record of its own entitlement of cpu time. Most of the rest
of these details apply to non-realtime tasks as rt task management is
straight forward.
Each runqueue keeps a record of what major epoch it is up to in the
rq->prio_rotation field which is incremented on each major epoch. It also
keeps a record of quota available to each priority value valid for that
major epoch in rq->prio_quota[].
Each task keeps a record of what major runqueue epoch it was last running
on in p->rotation. It also keeps a record of what priority levels it has
already been allocated quota from during this epoch in a bitmap p->bitmap.
The only tunable that determines all other details is the RR_INTERVAL. This
is set to 8ms (minimum on 1000HZ, higher at different HZ values), and is
scaled gently upwards with more cpus.
All tasks are initially given a quota based on RR_INTERVAL. This is equal to
RR_INTERVAL between nice values of 0 and 19, and progressively larger for nice
values from -1 to -20. This is to maintain a relationship of nice 19 having
approximately 1/20th of the cpu of nice 0, and nice 0 having 1/20th the cpu of
nice -20. This is assigned to p->quota and only changes with changes in nice
level.
As a task is first queued, it checks in recalc_task_prio to see if it has run at
this runqueue's current priority rotation. If it has not, it will have its
p->prio level set according to the first slot in a "priority matrix" and will be
given a p->time_slice equal to the p->quota, and has its allocation bitmap bit
set in p->bitmap for this prio level. This quota is then also added to the
current runqueue's rq->prio_quota[p->prio]. It is then queued on the current
active priority array.
If a task has already been running during this major epoch, and it has
p->time_slice left and the rq->prio_quota for the task's p->prio still
has quota, it will be placed back on the active array, but no more quota
will be added to either the task or the runqueue quota.
If a task has been running during this major epoch, but does not have
p->time_slice left or the runqueue's prio_quota for this task's p->prio
does not have quota, it will find the next lowest priority in its bitmap
that it has not been allocated quota from. It then gets the a full quota
in p->time_slice and adds that to the quota value for the relevant priority
rq->prio_quota. It is then queued on the current active priority array at
the newly determined lower priority.
If a task has been running during this major epoch, and does not have
any entitlement left in p->bitmap and no time_slice left, it will have its
bitmap cleared, and be queued at its p->static_prio again, but on the expired
priority array. No quota will be allocated until this task is scheduled.
When a task is queued, it has its relevant bit set in the array->prio_bitmap.
During a scheduler_tick where a task is running, the p->time_slice is
decremented, and if it reaches zero then the recalc_task_prio is readjusted
and the task rescheduled.
During a task running tick, the runqueue prio_quota is also decremented. If
it empties then a priority rotation occurs (a major or minor epoch). If the
current runqueue's priority level is better than that of nice 19 tasks, a
minor rotation is performed, otherwise a major rotation will occur.
A minor rotation takes the remaining tasks at this priority level queue and
merges them with a list_splice_tail with the queue from the next lowest
priority level. At this time, any tasks that have been merged will now
have invalid values in p->prio so this must be considered when dequeueing
and scheduling the task.
A major rotation takes the remaining tasks at this priority level queue and
merges them with a list_splice_tail with the best priority task running on
the expired array, and swaps the priority arrays. The priority quotas are
reset at this time. Any tasks that have been merged will now have invalid
values in p->array and possibly p->prio so this must be considered. The
rq->prio_rotation is incremented at this time.
When a task is dequeued, the dyn_bitmap bit is unset only after testing
that the relevant queue is actually empty since p->prio may be inaccurate
and no hard accounting of the number of tasks at that level is possible.
When selecting a new task for scheduling, after the first dynamic bit is found
on the dyn_bitmap, it is checked to see that a task is really queued at that
priority or if it is a false positive due to the task being dequeued at a time
when its p->prio does not match which queue it is on after some form of priority
rotation. This is a rare occurrence as it tends to only occur if a task that is
already waiting on a runqueue gets dequeued. If no tasks remain on the active
array, a major priority rotation is performed. If the chosen task has not been
running during this major or minor rotation it has new quota allocated at this
time, and added to the runqueue's quota.
If a task finds itself merged at a priority level that it does not normally
receive quota at (due to list merging) it will remove one of its normal
priority slots to compensate.
Priority Matrix
===============
In order to minimise the latencies between tasks of different nice levels
running concurrently, the dynamic priority slots where different nice levels
are queued are dithered instead of being sequential. What this means is that
there are 40 priority slots where a task may run during one major rotation,
and the allocation of slots is dependant on nice level. In the
following table, a zero represents a slot where the task may run.
nice -20 0000000000000000000000000000000000000000
nice -10 1001000100100010001001000100010010001000
nice 0 0101010101010101010101010101010101010101
nice 5 1101011010110101101011010110101101011011
nice 10 0110111011011101110110111011101101110111
nice 15 0111110111111011111101111101111110111111
nice 19 1111111111111111111011111111111111111111
As can be seen, a nice -20 task runs in every priority slot whereas a nice 19
task only runs one slot per major rotation. This dithered table allows for the
smallest possible maximum latencies between tasks of varying nice levels, thus
allowing vastly different nice levels to be used.
Modelling deadline behaviour
============================
As the accounting in this design is hard and not modified by sleep average
calculations or interactivity modifiers, it is possible to accurately
predict the maximum latency that a task may experience under different
conditions. This is a virtual deadline mechanism enforced by mandatory
runqueue epochs, and not by trying to keep complicated accounting of each
task.
The maximum duration a task can run during one major epoch is determined by its
nice value. Nice 0 tasks can run at 19 different priority levels for RR_INTERVAL
duration during each epoch. Nice 10 tasks can run at 9 priority levels for each
epoch, and so on. The table in the priority matrix above demonstrates how this
is enforced.
Therefore the maximum duration a runqueue epoch can take is determined by
the number of tasks running, and their nice level. After that, the maximum
duration it can take before a task can wait before it get scheduled is
determined by the position of its first slot on the matrix.
In the following examples, these are _worst case scenarios_ and would rarely
occur, but can be modelled nonetheless to determine the maximum possible
latency.
So for example, if two nice 0 tasks are running, and one has just expired as
another is activated for the first time receiving a full quota for this
runqueue rotation, the first task will wait:
nr_tasks * max_duration + nice_difference * rr_interval
1 * 19 * RR_INTERVAL + 0 = 152ms
In the presence of a nice 10 task, a nice 0 task would wait a maximum of
1 * 10 * RR_INTERVAL + 0 = 80ms
In the presence of a nice 0 task, a nice 10 task would wait a maximum of
1 * 19 * RR_INTERVAL + 1 * RR_INTERVAL = 160ms
More useful than these values, though, are the average latencies which are
a matter of determining the average distance between priority slots of
different nice values and multiplying them by the tasks' quota. For example
in the presence of a nice -10 task, a nice 0 task will wait either one or
two slots. Given that nice -10 tasks have a quota 2.5 times the RR_INTERVAL,
this means the latencies will alternate between 2.5 and 5 RR_INTERVALs or
20 and 40ms respectively (on uniprocessor at 1000HZ).
Achieving interactivity
=======================
A requirement of this scheduler design was to achieve good interactivity
despite being a completely fair deadline based design. The disadvantage of
designs that try to achieve interactivity is that they usually do so at
the expense of maintaining fairness. As cpu speeds increase, the requirement
for some sort of metered unfairness towards interactive tasks becomes a less
desirable phenomenon, but low latency and fairness remains mandatory to
good interactive performance.
This design relies on the fact that interactive tasks, by their nature,
sleep often. Most fair scheduling designs end up penalising such tasks
indirectly giving them less than their fair possible share because of the
sleep, and have to use a mechanism of bonusing their priority to offset
this based on the duration they sleep. This becomes increasingly inaccurate
as the number of running tasks rises and more tasks spend time waiting on
runqueues rather than sleeping, and it is impossible to tell whether the
task that's waiting on a runqueue only intends to run for a short period and
then sleep again after than runqueue wait. Furthermore, all such designs rely
on a period of time to pass to accumulate some form of statistic on the task
before deciding on how much to give them preference. The shorter this period,
the more rapidly bursts of cpu ruin the interactive tasks behaviour. The
longer this period, the longer it takes for interactive tasks to get low
scheduling latencies and fair cpu.
This design does not measure sleep time at all. Interactive tasks that sleep
often will wake up having consumed very little if any of their quota for
the current major priority rotation. The longer they have slept, the less
likely they are to even be on the current major priority rotation. Once
woken up, though, they get to use up a their full quota for that epoch,
whether part of a quota remains or a full quota. Overall, however, they
can still only run as much cpu time for that epoch as any other task of the
same nice level. This means that two tasks behaving completely differently
from fully cpu bound to waking/sleeping extremely frequently will still
get the same quota of cpu, but the latter will be using its quota for that
epoch in bursts rather than continuously. This guarantees that interactive
tasks get the same amount of cpu as cpu bound ones.
The other requirement of interactive tasks is also to obtain low latencies
for when they are scheduled. Unlike fully cpu bound tasks and the maximum
latencies possible described in the modelling deadline behaviour section
above, tasks that sleep will wake up with quota available usually at the
current runqueue's priority_level or better. This means that the most latency
they are likely to see is one RR_INTERVAL, and often they will preempt the
current task if it is not of a sleeping nature. This then guarantees very
low latency for interactive tasks, and the lowest latencies for the least
cpu bound tasks.
One of the potential disadvantages of a strict fairness design is that users
may prefer a degree of unfairness towards certain tasks (such as a gui) and
will notice the relative slowdown that occurs under load. As the dithered
matrix minimises the latencies when differential nice levels are used, this
can be countered by running a gui at a negative nice value such as -10 without
causing adversely large latencies in nice 0 tasks.
Signed-off-by: Con Kolivas <kernel@...ivas.org>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Nick Piggin <nickpiggin@...oo.com.au>
Cc: "Siddha, Suresh B" <suresh.b.siddha@...el.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---
include/linux/init_task.h | 2
include/linux/sched.h | 32 -
kernel/sched.c | 1221 ++++++++++++++++++++++------------------------
3 files changed, 629 insertions(+), 626 deletions(-)
Index: linux-2.6.21-rc3-mm2/include/linux/init_task.h
===================================================================
--- linux-2.6.21-rc3-mm2.orig/include/linux/init_task.h 2007-03-16 23:27:49.000000000 +1100
+++ linux-2.6.21-rc3-mm2/include/linux/init_task.h 2007-03-16 23:27:51.000000000 +1100
@@ -110,6 +110,7 @@ extern struct group_info init_groups;
.prio = MAX_PRIO-20, \
.static_prio = MAX_PRIO-20, \
.normal_prio = MAX_PRIO-20, \
+ .rotation = 0, \
.policy = SCHED_NORMAL, \
.cpus_allowed = CPU_MASK_ALL, \
.mm = NULL, \
@@ -117,6 +118,7 @@ extern struct group_info init_groups;
.run_list = LIST_HEAD_INIT(tsk.run_list), \
.ioprio = 0, \
.time_slice = HZ, \
+ .quota = HZ, \
.tasks = LIST_HEAD_INIT(tsk.tasks), \
.parent = &tsk, \
.children = LIST_HEAD_INIT(tsk.children), \
Index: linux-2.6.21-rc3-mm2/include/linux/sched.h
===================================================================
--- linux-2.6.21-rc3-mm2.orig/include/linux/sched.h 2007-03-16 23:27:51.000000000 +1100
+++ linux-2.6.21-rc3-mm2/include/linux/sched.h 2007-03-16 23:27:51.000000000 +1100
@@ -530,8 +530,9 @@ struct signal_struct {
#define MAX_USER_RT_PRIO 100
#define MAX_RT_PRIO MAX_USER_RT_PRIO
+#define PRIO_RANGE (40)
-#define MAX_PRIO (MAX_RT_PRIO + 40)
+#define MAX_PRIO (MAX_RT_PRIO + PRIO_RANGE)
#define rt_prio(prio) unlikely((prio) < MAX_RT_PRIO)
#define rt_task(p) rt_prio((p)->prio)
@@ -815,13 +816,6 @@ struct mempolicy;
struct pipe_inode_info;
struct uts_namespace;
-enum sleep_type {
- SLEEP_NORMAL,
- SLEEP_NONINTERACTIVE,
- SLEEP_INTERACTIVE,
- SLEEP_INTERRUPTED,
-};
-
struct prio_array;
struct task_struct {
@@ -840,20 +834,36 @@ struct task_struct {
int load_weight; /* for niceness load balancing purposes */
int prio, static_prio, normal_prio;
struct list_head run_list;
+ DECLARE_BITMAP(bitmap, PRIO_RANGE + 1);
+ /*
+ * This bitmap shows what priorities this task has received quota
+ * from for this major priority rotation on its current runqueue.
+ */
struct prio_array *array;
+ unsigned long rotation;
+ /* Which major runqueue rotation did this task run */
unsigned short ioprio;
#ifdef CONFIG_BLK_DEV_IO_TRACE
unsigned int btrace_seq;
#endif
- unsigned long sleep_avg;
unsigned long long timestamp, last_ran;
unsigned long long sched_time; /* sched_clock time spent running */
- enum sleep_type sleep_type;
unsigned int policy;
cpumask_t cpus_allowed;
- unsigned int time_slice, first_time_slice;
+ unsigned int time_slice;
+ /*
+ * How much this task is entitled to run at the current priority
+ * before being requeued at a lower priority.
+ */
+ unsigned int first_time_slice;
+ /* Is this the very first time_slice this task has ever run. */
+ unsigned int quota;
+ /*
+ * How much this task contributes to the current priority queue
+ * length
+ */
#ifdef CONFIG_PREEMPT_RCU
int rcu_read_lock_nesting;
Index: linux-2.6.21-rc3-mm2/kernel/sched.c
===================================================================
--- linux-2.6.21-rc3-mm2.orig/kernel/sched.c 2007-03-16 23:27:49.000000000 +1100
+++ linux-2.6.21-rc3-mm2/kernel/sched.c 2007-03-16 23:27:51.000000000 +1100
@@ -16,6 +16,7 @@
* by Davide Libenzi, preemptible kernel bits by Robert Love.
* 2003-09-03 Interactivity tuning by Con Kolivas.
* 2004-04-02 Scheduler domains code by Nick Piggin
+ * 2007-03-02 Rotating Staircase deadline scheduling policy by Con Kolivas
*/
#include <linux/mm.h>
@@ -85,103 +86,35 @@ unsigned long long __attribute__((weak))
#define USER_PRIO(p) ((p)-MAX_RT_PRIO)
#define TASK_USER_PRIO(p) USER_PRIO((p)->static_prio)
#define MAX_USER_PRIO (USER_PRIO(MAX_PRIO))
+#define SCHED_PRIO(p) ((p)+MAX_RT_PRIO)
-/*
- * Some helpers for converting nanosecond timing to jiffy resolution
- */
-#define NS_TO_JIFFIES(TIME) ((TIME) / (1000000000 / HZ))
-#define JIFFIES_TO_NS(TIME) ((TIME) * (1000000000 / HZ))
-
-/*
- * These are the 'tuning knobs' of the scheduler:
- *
- * Minimum timeslice is 5 msecs (or 1 jiffy, whichever is larger),
- * default timeslice is 100 msecs, maximum timeslice is 800 msecs.
- * Timeslices get refilled after they expire.
- */
-#define MIN_TIMESLICE max(5 * HZ / 1000, 1)
-#define DEF_TIMESLICE (100 * HZ / 1000)
-#define ON_RUNQUEUE_WEIGHT 30
-#define CHILD_PENALTY 95
-#define PARENT_PENALTY 100
-#define EXIT_WEIGHT 3
-#define PRIO_BONUS_RATIO 25
-#define MAX_BONUS (MAX_USER_PRIO * PRIO_BONUS_RATIO / 100)
-#define INTERACTIVE_DELTA 2
-#define MAX_SLEEP_AVG (DEF_TIMESLICE * MAX_BONUS)
-#define STARVATION_LIMIT (MAX_SLEEP_AVG)
-#define NS_MAX_SLEEP_AVG (JIFFIES_TO_NS(MAX_SLEEP_AVG))
+#define TASK_PREEMPTS_CURR(p, curr) ((p)->prio < (curr)->prio)
/*
- * If a task is 'interactive' then we reinsert it in the active
- * array after it has expired its current timeslice. (it will not
- * continue to run immediately, it will still roundrobin with
- * other interactive tasks.)
- *
- * This part scales the interactivity limit depending on niceness.
- *
- * We scale it linearly, offset by the INTERACTIVE_DELTA delta.
- * Here are a few examples of different nice levels:
- *
- * TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0]
- * TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0]
- * TASK_INTERACTIVE( 0): [1,1,1,1,0,0,0,0,0,0,0]
- * TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0]
- * TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0]
- *
- * (the X axis represents the possible -5 ... 0 ... +5 dynamic
- * priority range a task can explore, a value of '1' means the
- * task is rated interactive.)
- *
- * Ie. nice +19 tasks can never get 'interactive' enough to be
- * reinserted into the active array. And only heavily CPU-hog nice -20
- * tasks will be expired. Default nice 0 tasks are somewhere between,
- * it takes some effort for them to get interactive, but it's not
- * too hard.
+ * This is the time all tasks within the same priority round robin.
+ * Set to a minimum of 8ms. Scales with number of cpus and rounds with HZ.
*/
-
-#define CURRENT_BONUS(p) \
- (NS_TO_JIFFIES((p)->sleep_avg) * MAX_BONUS / \
- MAX_SLEEP_AVG)
-
-#define GRANULARITY (10 * HZ / 1000 ? : 1)
-
-#ifdef CONFIG_SMP
-#define TIMESLICE_GRANULARITY(p) (GRANULARITY * \
- (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)) * \
- num_online_cpus())
-#else
-#define TIMESLICE_GRANULARITY(p) (GRANULARITY * \
- (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)))
-#endif
-
-#define SCALE(v1,v1_max,v2_max) \
- (v1) * (v2_max) / (v1_max)
-
-#define DELTA(p) \
- (SCALE(TASK_NICE(p) + 20, 40, MAX_BONUS) - 20 * MAX_BONUS / 40 + \
- INTERACTIVE_DELTA)
-
-#define TASK_INTERACTIVE(p) \
- ((p)->prio <= (p)->static_prio - DELTA(p))
-
-#define INTERACTIVE_SLEEP(p) \
- (JIFFIES_TO_NS(MAX_SLEEP_AVG * \
- (MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))
-
-#define TASK_PREEMPTS_CURR(p, rq) \
- ((p)->prio < (rq)->curr->prio)
-
-#define SCALE_PRIO(x, prio) \
- max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_TIMESLICE)
-
-static unsigned int static_prio_timeslice(int static_prio)
-{
- if (static_prio < NICE_TO_PRIO(0))
- return SCALE_PRIO(DEF_TIMESLICE * 4, static_prio);
- else
- return SCALE_PRIO(DEF_TIMESLICE, static_prio);
-}
+static unsigned int rr_interval __read_mostly;
+#define RR_INTERVAL 8
+#define DEF_TIMESLICE (rr_interval * 20)
+
+/*
+ * This contains a bitmap for each dynamic priority level with empty slots
+ * for the valid priorities each different nice level can have. It allows
+ * us to stagger the slots where differing priorities run in a way that
+ * keeps latency differences between different nice levels at a minimum.
+ * ie, where 0 means a slot for that priority, priority running from left to
+ * right:
+ * nice -20 0000000000000000000000000000000000000000
+ * nice -10 1001000100100010001001000100010010001000
+ * nice 0 0101010101010101010101010101010101010101
+ * nice 5 1101011010110101101011010110101101011011
+ * nice 10 0110111011011101110110111011101101110111
+ * nice 15 0111110111111011111101111101111110111111
+ * nice 19 1111111111111111111011111111111111111111
+ */
+static unsigned long prio_matrix[PRIO_RANGE][BITS_TO_LONGS(PRIO_RANGE)]
+ __read_mostly;
#ifdef CONFIG_SMP
/*
@@ -205,27 +138,17 @@ static inline void sg_inc_cpu_power(stru
#endif
/*
- * task_timeslice() scales user-nice values [ -20 ... 0 ... 19 ]
- * to time slice values: [800ms ... 100ms ... 5ms]
- *
- * The higher a thread's priority, the bigger timeslices
- * it gets during one round of execution. But even the lowest
- * priority thread gets MIN_TIMESLICE worth of execution time.
- */
-
-static inline unsigned int task_timeslice(struct task_struct *p)
-{
- return static_prio_timeslice(p->static_prio);
-}
-
-/*
* These are the runqueue data structures:
*/
-
struct prio_array {
- unsigned int nr_active;
- DECLARE_BITMAP(bitmap, MAX_PRIO+1); /* include 1 bit for delimiter */
struct list_head queue[MAX_PRIO];
+ /* Tasks queued at each priority */
+
+ DECLARE_BITMAP(prio_bitmap, MAX_PRIO + 1);
+ /*
+ * The bitmap of priorities queued; The dynamic bits can have
+ * false positives. Include 1 bit for delimiter.
+ */
};
/*
@@ -261,14 +184,27 @@ struct rq {
*/
unsigned long nr_uninterruptible;
- unsigned long expired_timestamp;
/* Cached timestamp set by update_cpu_clock() */
unsigned long long most_recent_timestamp;
struct task_struct *curr, *idle;
unsigned long next_balance;
struct mm_struct *prev_mm;
+
+ long prio_quota[PRIO_RANGE];
+ /*
+ * The quota of ticks the runqueue runs at each dynamic priority
+ * before cycling to the next priority.
+ */
+
struct prio_array *active, *expired, arrays[2];
- int best_expired_prio;
+ unsigned long *dyn_bitmap, *exp_bitmap;
+
+ int prio_level;
+ /* The current dynamic priority level this runqueue is at */
+
+ unsigned long prio_rotation;
+ /* How many times we have rotated the priority queue */
+
atomic_t nr_iowait;
#ifdef CONFIG_SMP
@@ -607,12 +543,9 @@ static inline struct rq *this_rq_lock(vo
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
/*
* Called when a process is dequeued from the active array and given
- * the cpu. We should note that with the exception of interactive
- * tasks, the expired queue will become the active queue after the active
- * queue is empty, without explicitly dequeuing and requeuing tasks in the
- * expired queue. (Interactive tasks may be requeued directly to the
- * active queue, thus delaying tasks in the expired queue from running;
- * see scheduler_tick()).
+ * the cpu. We should note that the expired queue will become the active
+ * queue after the active queue is empty, without explicitly dequeuing and
+ * requeuing tasks in the expired queue.
*
* This function is only called from sched_info_arrive(), rather than
* dequeue_task(). Even though a task may be queued and dequeued multiple
@@ -710,71 +643,168 @@ sched_info_switch(struct task_struct *pr
#define sched_info_switch(t, next) do { } while (0)
#endif /* CONFIG_SCHEDSTATS || CONFIG_TASK_DELAY_ACCT */
+static inline int task_queued(struct task_struct *task)
+{
+ return !list_empty(&task->run_list);
+}
+
+static inline void set_task_entitlement(struct task_struct *p)
+{
+ __set_bit(USER_PRIO(p->prio), p->bitmap);
+ p->time_slice = p->quota;
+}
+
/*
- * Adding/removing a task to/from a priority array:
+ * There is no specific hard accounting. The dynamic bits can have
+ * false positives. rt_tasks can only be on the active queue.
*/
-static void dequeue_task(struct task_struct *p, struct prio_array *array)
+static inline void set_dynamic_bit(struct task_struct *p, struct rq *rq)
{
- array->nr_active--;
- list_del(&p->run_list);
- if (list_empty(array->queue + p->prio))
- __clear_bit(p->prio, array->bitmap);
+ __set_bit(p->prio, p->array->prio_bitmap);
}
-static void enqueue_task(struct task_struct *p, struct prio_array *array)
+/*
+ * Removing from a runqueue. While we don't know with absolute certainty
+ * where this task really is, the p->array and p->prio are very likely
+ * so we check that queue to see if we can clear that bit to take some
+ * load off finding false positives in next_dynamic_task().
+ */
+static void dequeue_task(struct task_struct *p, struct rq *rq)
{
- sched_info_queued(p);
- list_add_tail(&p->run_list, array->queue + p->prio);
- __set_bit(p->prio, array->bitmap);
- array->nr_active++;
- p->array = array;
+ list_del_init(&p->run_list);
+ if (list_empty(p->array->queue + p->prio))
+ __clear_bit(p->prio, p->array->prio_bitmap);
}
/*
- * Put task to the end of the run list without the overhead of dequeue
- * followed by enqueue.
+ * The task is being queued on a fresh array so it has its entitlement
+ * bitmap cleared.
*/
-static void requeue_task(struct task_struct *p, struct prio_array *array)
+static inline void task_new_array(struct task_struct *p, struct rq *rq)
{
- list_move_tail(&p->run_list, array->queue + p->prio);
+ bitmap_zero(p->bitmap, PRIO_RANGE);
+ p->rotation = rq->prio_rotation;
}
-static inline void
-enqueue_task_head(struct task_struct *p, struct prio_array *array)
+static inline int first_prio_slot(struct task_struct *p)
+{
+ return SCHED_PRIO(find_first_zero_bit(
+ prio_matrix[USER_PRIO(p->static_prio)], PRIO_RANGE));
+}
+
+static inline int next_prio_slot(struct task_struct *p, int prio)
+{
+ DECLARE_BITMAP(tmp, PRIO_RANGE);
+ bitmap_or(tmp, p->bitmap, prio_matrix[USER_PRIO(p->static_prio)],
+ PRIO_RANGE);
+ return SCHED_PRIO(find_next_zero_bit(tmp, PRIO_RANGE,
+ USER_PRIO(prio)));
+}
+
+static void queue_expired(struct task_struct *p, struct rq *rq)
+{
+ p->array = rq->expired;
+ task_new_array(p, rq);
+ p->prio = p->normal_prio = first_prio_slot(p);
+ p->time_slice = p->quota;
+}
+
+#define rq_quota(rq, prio) ((rq)->prio_quota[USER_PRIO(prio)])
+
+/*
+ * recalc_task_prio determines what prio a non rt_task will be
+ * queued at. If the task has already been running during this runqueue's
+ * major rotation (rq->prio_rotation) then it continues at the same
+ * priority if it has tick entitlement left. If it does not have entitlement
+ * left, it finds the next priority slot according to its nice value that it
+ * has not extracted quota from. If it has not run during this major
+ * rotation, it starts at its static priority and has its bitmap quota
+ * cleared. If it does not have any slots left it has all its slots reset and
+ * is queued on the expired at its static priority.
+ */
+static void recalc_task_prio(struct task_struct *p, struct rq *rq)
{
- list_add(&p->run_list, array->queue + p->prio);
- __set_bit(p->prio, array->bitmap);
- array->nr_active++;
+ struct prio_array *array = rq->active;
+ int queue_prio, search_prio = MAX_RT_PRIO;
+
+ /*
+ * SCHED_BATCH tasks never start at better priority than any other
+ * task that is already running since they are flagged as latency
+ * insensitive. This means they never cause greater latencies in other
+ * non SCHED_BATCH tasks of the same nice level, but they still will
+ * not be exposed to high latencies themselves.
+ */
+ if (unlikely(p->policy == SCHED_BATCH))
+ search_prio = rq->prio_level;
+
+ if (p->rotation == rq->prio_rotation) {
+ if (p->array == array) {
+ if (p->time_slice && rq_quota(rq, p->prio))
+ return;
+ search_prio = p->prio;
+ } else if (p->array == rq->expired) {
+ queue_expired(p, rq);
+ return;
+ } else
+ task_new_array(p, rq);
+ } else
+ task_new_array(p, rq);
+
+ queue_prio = next_prio_slot(p, search_prio);
+ if (queue_prio >= MAX_PRIO) {
+ queue_expired(p, rq);
+ return;
+ }
+ rq_quota(rq, queue_prio) += p->quota;
+ p->prio = p->normal_prio = queue_prio;
p->array = array;
+ set_task_entitlement(p);
}
/*
- * __normal_prio - return the priority that is based on the static
- * priority but is modified by bonuses/penalties.
- *
- * We scale the actual sleep average [0 .... MAX_SLEEP_AVG]
- * into the -5 ... 0 ... +5 bonus/penalty range.
- *
- * We use 25% of the full 0...39 priority range so that:
- *
- * 1) nice +19 interactive tasks do not preempt nice 0 CPU hogs.
- * 2) nice -20 CPU hogs do not get preempted by nice 0 tasks.
- *
- * Both properties are important to certain workloads.
+ * Adding to a runqueue. The dynamic priority queue that it is added to is
+ * determined by the priority rotation of the runqueue it is being added to
+ * and the quota still available in the task in p->bitmap and p->time_slice
+ * (see recalc_task_prio above).
*/
+static inline void __enqueue_task(struct task_struct *p, struct rq *rq)
+{
+ if (rt_task(p))
+ p->array = rq->active;
+ else
+ recalc_task_prio(p, rq);
-static inline int __normal_prio(struct task_struct *p)
+ sched_info_queued(p);
+ set_dynamic_bit(p, rq);
+}
+
+static void enqueue_task(struct task_struct *p, struct rq *rq)
{
- int bonus, prio;
+ __enqueue_task(p, rq);
+ list_add_tail(&p->run_list, p->array->queue + p->prio);
+}
- bonus = CURRENT_BONUS(p) - MAX_BONUS / 2;
+static inline void enqueue_task_head(struct task_struct *p, struct rq *rq)
+{
+ __enqueue_task(p, rq);
+ list_add(&p->run_list, p->array->queue + p->prio);
+}
- prio = p->static_prio - bonus;
- if (prio < MAX_RT_PRIO)
- prio = MAX_RT_PRIO;
- if (prio > MAX_PRIO-1)
- prio = MAX_PRIO-1;
- return prio;
+/*
+ * requeue_task is only called when p->static_prio does not change. p->prio
+ * can change with dynamic tasks.
+ */
+static void requeue_task(struct task_struct *p, struct rq *rq,
+ struct prio_array *old_array, int old_prio)
+{
+ if (p->array == rq->expired)
+ queue_expired(p, rq);
+ list_move_tail(&p->run_list, p->array->queue + p->prio);
+ if (!rt_task(p)) {
+ if (list_empty(old_array->queue + old_prio))
+ __clear_bit(old_prio, p->array->prio_bitmap);
+ set_dynamic_bit(p, rq);
+ }
}
/*
@@ -787,6 +817,20 @@ static inline int __normal_prio(struct t
*/
/*
+ * task_timeslice - the total duration a task can run during one major
+ * rotation.
+ */
+static inline unsigned int task_timeslice(struct task_struct *p)
+{
+ unsigned int slice, rr;
+
+ slice = rr = p->quota;
+ if (!rt_task(p))
+ slice += (PRIO_RANGE - 1 - TASK_USER_PRIO(p)) * rr;
+ return slice;
+}
+
+/*
* Assume: static_prio_timeslice(NICE_TO_PRIO(0)) == DEF_TIMESLICE
* If static_prio_timeslice() is ever changed to break this assumption then
* this code will need modification
@@ -794,10 +838,9 @@ static inline int __normal_prio(struct t
#define TIME_SLICE_NICE_ZERO DEF_TIMESLICE
#define LOAD_WEIGHT(lp) \
(((lp) * SCHED_LOAD_SCALE) / TIME_SLICE_NICE_ZERO)
-#define PRIO_TO_LOAD_WEIGHT(prio) \
- LOAD_WEIGHT(static_prio_timeslice(prio))
-#define RTPRIO_TO_LOAD_WEIGHT(rp) \
- (PRIO_TO_LOAD_WEIGHT(MAX_RT_PRIO) + LOAD_WEIGHT(rp))
+#define TASK_LOAD_WEIGHT(p) LOAD_WEIGHT(task_timeslice(p))
+#define RTPRIO_TO_LOAD_WEIGHT(rp) \
+ (LOAD_WEIGHT((rr_interval + 20 + (rp))))
static void set_load_weight(struct task_struct *p)
{
@@ -814,7 +857,7 @@ static void set_load_weight(struct task_
#endif
p->load_weight = RTPRIO_TO_LOAD_WEIGHT(p->rt_priority);
} else
- p->load_weight = PRIO_TO_LOAD_WEIGHT(p->static_prio);
+ p->load_weight = TASK_LOAD_WEIGHT(p);
}
static inline void
@@ -842,28 +885,38 @@ static inline void dec_nr_running(struct
}
/*
- * Calculate the expected normal priority: i.e. priority
- * without taking RT-inheritance into account. Might be
- * boosted by interactivity modifiers. Changes upon fork,
- * setprio syscalls, and whenever the interactivity
- * estimator recalculates.
+ * __activate_task - move a task to the runqueue.
*/
-static inline int normal_prio(struct task_struct *p)
+static inline void __activate_task(struct task_struct *p, struct rq *rq)
{
- int prio;
+ enqueue_task(p, rq);
+ inc_nr_running(p, rq);
+}
+
+/*
+ * __activate_idle_task - move idle task to the _front_ of runqueue.
+ */
+static inline void __activate_idle_task(struct task_struct *p, struct rq *rq)
+{
+ enqueue_task_head(p, rq);
+ inc_nr_running(p, rq);
+}
+static inline int normal_prio(struct task_struct *p)
+{
if (has_rt_policy(p))
- prio = MAX_RT_PRIO-1 - p->rt_priority;
+ return MAX_RT_PRIO-1 - p->rt_priority;
+ /* Other tasks all have normal_prio set in recalc_task_prio */
+ if (likely(p->prio >= MAX_RT_PRIO))
+ return p->prio;
else
- prio = __normal_prio(p);
- return prio;
+ return p->static_prio;
}
/*
* Calculate the current priority, i.e. the priority
* taken into account by the scheduler. This value might
- * be boosted by RT tasks, or might be boosted by
- * interactivity modifiers. Will be RT if the task got
+ * be boosted by RT tasks as it will be RT if the task got
* RT-boosted. If not then it returns p->normal_prio.
*/
static int effective_prio(struct task_struct *p)
@@ -880,111 +933,31 @@ static int effective_prio(struct task_st
}
/*
- * __activate_task - move a task to the runqueue.
- */
-static void __activate_task(struct task_struct *p, struct rq *rq)
-{
- struct prio_array *target = rq->active;
-
- if (batch_task(p))
- target = rq->expired;
- enqueue_task(p, target);
- inc_nr_running(p, rq);
-}
-
-/*
- * __activate_idle_task - move idle task to the _front_ of runqueue.
- */
-static inline void __activate_idle_task(struct task_struct *p, struct rq *rq)
-{
- enqueue_task_head(p, rq->active);
- inc_nr_running(p, rq);
-}
-
-/*
- * Recalculate p->normal_prio and p->prio after having slept,
- * updating the sleep-average too:
- */
-static int recalc_task_prio(struct task_struct *p, unsigned long long now)
-{
- /* Caller must always ensure 'now >= p->timestamp' */
- unsigned long sleep_time = now - p->timestamp;
-
- if (batch_task(p))
- sleep_time = 0;
-
- if (likely(sleep_time > 0)) {
- /*
- * This ceiling is set to the lowest priority that would allow
- * a task to be reinserted into the active array on timeslice
- * completion.
- */
- unsigned long ceiling = INTERACTIVE_SLEEP(p);
-
- if (p->mm && sleep_time > ceiling && p->sleep_avg < ceiling) {
- /*
- * Prevents user tasks from achieving best priority
- * with one single large enough sleep.
- */
- p->sleep_avg = ceiling;
- /*
- * Using INTERACTIVE_SLEEP() as a ceiling places a
- * nice(0) task 1ms sleep away from promotion, and
- * gives it 700ms to round-robin with no chance of
- * being demoted. This is more than generous, so
- * mark this sleep as non-interactive to prevent the
- * on-runqueue bonus logic from intervening should
- * this task not receive cpu immediately.
- */
- p->sleep_type = SLEEP_NONINTERACTIVE;
- } else {
- /*
- * Tasks waking from uninterruptible sleep are
- * limited in their sleep_avg rise as they
- * are likely to be waiting on I/O
- */
- if (p->sleep_type == SLEEP_NONINTERACTIVE && p->mm) {
- if (p->sleep_avg >= ceiling)
- sleep_time = 0;
- else if (p->sleep_avg + sleep_time >=
- ceiling) {
- p->sleep_avg = ceiling;
- sleep_time = 0;
- }
- }
-
- /*
- * This code gives a bonus to interactive tasks.
- *
- * The boost works by updating the 'average sleep time'
- * value here, based on ->timestamp. The more time a
- * task spends sleeping, the higher the average gets -
- * and the higher the priority boost gets as well.
- */
- p->sleep_avg += sleep_time;
-
- }
- if (p->sleep_avg > NS_MAX_SLEEP_AVG)
- p->sleep_avg = NS_MAX_SLEEP_AVG;
+ * All tasks have quotas based on rr_interval. From nice 0 to 19 they are
+ * all equal to it and below zero they get exponentially larger making their
+ * effective quota significantly larger. rt tasks all get rr_interval.
+ * ie nice -6..19 = rr_interval. nice -10 = 2.5 * rr_interval
+ * nice -20 = 10 * rr_interval. This makes the ratios between -20 and 0
+ * similar to the ratios between 0 and +19.
+ */
+static unsigned int rr_quota(struct task_struct *p)
+{
+ int neg_nice = -TASK_NICE(p), rr = rr_interval;
+
+ if (neg_nice > 6 && !rt_task(p)) {
+ rr *= neg_nice * neg_nice;
+ rr /= 40;
}
-
- return effective_prio(p);
+ return rr;
}
/*
* activate_task - move a task to the runqueue and do priority recalculation
- *
- * Update all the scheduling statistics stuff. (sleep average
- * calculation, priority modifiers, etc.)
*/
static void activate_task(struct task_struct *p, struct rq *rq, int local)
{
- unsigned long long now;
-
- if (rt_task(p))
- goto out;
+ unsigned long long now = sched_clock();
- now = sched_clock();
#ifdef CONFIG_SMP
if (!local) {
/* Compensate for drifting sched_clock */
@@ -1005,32 +978,9 @@ static void activate_task(struct task_st
(now - p->timestamp) >> 20);
}
- p->prio = recalc_task_prio(p, now);
-
- /*
- * This checks to make sure it's not an uninterruptible task
- * that is now waking up.
- */
- if (p->sleep_type == SLEEP_NORMAL) {
- /*
- * Tasks which were woken up by interrupts (ie. hw events)
- * are most likely of interactive nature. So we give them
- * the credit of extending their sleep time to the period
- * of time they spend on the runqueue, waiting for execution
- * on a CPU, first time around:
- */
- if (in_interrupt())
- p->sleep_type = SLEEP_INTERRUPTED;
- else {
- /*
- * Normal first-time wakeups get a credit too for
- * on-runqueue time, but it will be weighted down:
- */
- p->sleep_type = SLEEP_INTERACTIVE;
- }
- }
+ p->quota = rr_quota(p);
+ p->prio = effective_prio(p);
p->timestamp = now;
-out:
__activate_task(p, rq);
}
@@ -1040,8 +990,7 @@ out:
static void deactivate_task(struct task_struct *p, struct rq *rq)
{
dec_nr_running(p, rq);
- dequeue_task(p, p->array);
- p->array = NULL;
+ dequeue_task(p, rq);
}
/*
@@ -1134,7 +1083,7 @@ migrate_task(struct task_struct *p, int
* If the task is not on a runqueue (and not running), then
* it is sufficient to simply update the task's cpu field.
*/
- if (!p->array && !task_running(rq, p)) {
+ if (!task_queued(p) && !task_running(rq, p)) {
set_task_cpu(p, dest_cpu);
return 0;
}
@@ -1165,7 +1114,7 @@ void wait_task_inactive(struct task_stru
repeat:
rq = task_rq_lock(p, &flags);
/* Must be off runqueue entirely, not preempted. */
- if (unlikely(p->array || task_running(rq, p))) {
+ if (unlikely(task_queued(p) || task_running(rq, p))) {
/* If it's preempted, we yield. It could be a while. */
preempted = !task_running(rq, p);
task_rq_unlock(rq, &flags);
@@ -1440,6 +1389,31 @@ static inline int wake_idle(int cpu, str
}
#endif
+/*
+ * We need to have a special definition for an idle runqueue when testing
+ * for preemption on CONFIG_HOTPLUG_CPU as the idle task may be scheduled as
+ * a realtime task in sched_idle_next.
+ */
+#ifdef CONFIG_HOTPLUG_CPU
+#define rq_idle(rq) ((rq)->curr == (rq)->idle && !rt_task((rq)->curr))
+#else
+#define rq_idle(rq) ((rq)->curr == (rq)->idle)
+#endif
+
+static inline int task_preempts_curr(struct task_struct *p, struct rq *rq)
+{
+ struct task_struct *curr = rq->curr;
+
+ return ((p->array == task_rq(p)->active &&
+ TASK_PREEMPTS_CURR(p, curr)) || rq_idle(rq));
+}
+
+static inline void try_preempt(struct task_struct *p, struct rq *rq)
+{
+ if (task_preempts_curr(p, rq))
+ resched_task(rq->curr);
+}
+
/***
* try_to_wake_up - wake up a thread
* @p: the to-be-woken-up thread
@@ -1471,7 +1445,7 @@ static int try_to_wake_up(struct task_st
if (!(old_state & state))
goto out;
- if (p->array)
+ if (task_queued(p))
goto out_running;
cpu = task_cpu(p);
@@ -1564,7 +1538,7 @@ out_set_cpu:
old_state = p->state;
if (!(old_state & state))
goto out;
- if (p->array)
+ if (task_queued(p))
goto out_running;
this_cpu = smp_processor_id();
@@ -1573,26 +1547,10 @@ out_set_cpu:
out_activate:
#endif /* CONFIG_SMP */
- if (old_state == TASK_UNINTERRUPTIBLE) {
+ if (old_state == TASK_UNINTERRUPTIBLE)
rq->nr_uninterruptible--;
- /*
- * Tasks on involuntary sleep don't earn
- * sleep_avg beyond just interactive state.
- */
- p->sleep_type = SLEEP_NONINTERACTIVE;
- } else
/*
- * Tasks that have marked their sleep as noninteractive get
- * woken up with their sleep average not weighted in an
- * interactive way.
- */
- if (old_state & TASK_NONINTERACTIVE)
- p->sleep_type = SLEEP_NONINTERACTIVE;
-
-
- activate_task(p, rq, cpu == this_cpu);
- /*
* Sync wakeups (i.e. those types of wakeups where the waker
* has indicated that it will leave the CPU in short order)
* don't trigger a preemption, if the woken up task will run on
@@ -1600,10 +1558,9 @@ out_activate:
* the waker guarantees that the freshly woken up task is going
* to be considered on this CPU.)
*/
- if (!sync || cpu != this_cpu) {
- if (TASK_PREEMPTS_CURR(p, rq))
- resched_task(rq->curr);
- }
+ activate_task(p, rq, cpu == this_cpu);
+ if (!sync || cpu != this_cpu)
+ try_preempt(p, rq);
success = 1;
out_running:
@@ -1654,7 +1611,6 @@ void fastcall sched_fork(struct task_str
p->prio = current->normal_prio;
INIT_LIST_HEAD(&p->run_list);
- p->array = NULL;
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
if (unlikely(sched_info_on()))
memset(&p->sched_info, 0, sizeof(p->sched_info));
@@ -1666,6 +1622,8 @@ void fastcall sched_fork(struct task_str
/* Want to start with kernel preemption disabled. */
task_thread_info(p)->preempt_count = 1;
#endif
+ if (unlikely(p->policy == SCHED_FIFO))
+ goto out;
/*
* Share the timeslice between parent and child, thus the
* total amount of pending timeslices in the system doesn't change,
@@ -1680,16 +1638,17 @@ void fastcall sched_fork(struct task_str
p->first_time_slice = 1;
current->time_slice >>= 1;
p->timestamp = sched_clock();
- if (unlikely(!current->time_slice)) {
+ if (!current->time_slice) {
/*
- * This case is rare, it happens when the parent has only
- * a single jiffy left from its timeslice. Taking the
- * runqueue lock is not a problem.
+ * This case happens when the parent has only a single jiffy
+ * left from its timeslice. Taking the runqueue lock is not
+ * a problem.
*/
current->time_slice = 1;
task_running_tick(cpu_rq(cpu), current);
}
local_irq_enable();
+out:
put_cpu();
}
@@ -1711,38 +1670,16 @@ void fastcall wake_up_new_task(struct ta
this_cpu = smp_processor_id();
cpu = task_cpu(p);
- /*
- * We decrease the sleep average of forking parents
- * and children as well, to keep max-interactive tasks
- * from forking tasks that are max-interactive. The parent
- * (current) is done further down, under its lock.
- */
- p->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(p) *
- CHILD_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
-
- p->prio = effective_prio(p);
-
if (likely(cpu == this_cpu)) {
+ activate_task(p, rq, 1);
if (!(clone_flags & CLONE_VM)) {
/*
* The VM isn't cloned, so we're in a good position to
* do child-runs-first in anticipation of an exec. This
* usually avoids a lot of COW overhead.
*/
- if (unlikely(!current->array))
- __activate_task(p, rq);
- else {
- p->prio = current->prio;
- p->normal_prio = current->normal_prio;
- list_add_tail(&p->run_list, ¤t->run_list);
- p->array = current->array;
- p->array->nr_active++;
- inc_nr_running(p, rq);
- }
set_need_resched();
- } else
- /* Run child last */
- __activate_task(p, rq);
+ }
/*
* We skip the following code due to cpu == this_cpu
*
@@ -1759,19 +1696,16 @@ void fastcall wake_up_new_task(struct ta
*/
p->timestamp = (p->timestamp - this_rq->most_recent_timestamp)
+ rq->most_recent_timestamp;
- __activate_task(p, rq);
- if (TASK_PREEMPTS_CURR(p, rq))
- resched_task(rq->curr);
+ activate_task(p, rq, 0);
+ try_preempt(p, rq);
/*
* Parent and child are on different CPUs, now get the
- * parent runqueue to update the parent's ->sleep_avg:
+ * parent runqueue to update the parent's ->flags:
*/
task_rq_unlock(rq, &flags);
this_rq = task_rq_lock(current, &flags);
}
- current->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(current) *
- PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
task_rq_unlock(this_rq, &flags);
}
@@ -1789,20 +1723,12 @@ void fastcall sched_exit(struct task_str
unsigned long flags;
struct rq *rq;
- /*
- * If the child was a (relative-) CPU hog then decrease
- * the sleep_avg of the parent as well.
- */
rq = task_rq_lock(p->parent, &flags);
if (p->first_time_slice && task_cpu(p) == task_cpu(p->parent)) {
p->parent->time_slice += p->time_slice;
- if (unlikely(p->parent->time_slice > task_timeslice(p)))
- p->parent->time_slice = task_timeslice(p);
+ if (unlikely(p->parent->time_slice > p->quota))
+ p->parent->time_slice = p->quota;
}
- if (p->sleep_avg < p->parent->sleep_avg)
- p->parent->sleep_avg = p->parent->sleep_avg /
- (EXIT_WEIGHT + 1) * EXIT_WEIGHT + p->sleep_avg /
- (EXIT_WEIGHT + 1);
task_rq_unlock(rq, &flags);
}
@@ -2136,21 +2062,23 @@ void sched_exec(void)
*/
static void pull_task(struct rq *src_rq, struct prio_array *src_array,
struct task_struct *p, struct rq *this_rq,
- struct prio_array *this_array, int this_cpu)
+ int this_cpu)
{
- dequeue_task(p, src_array);
+ dequeue_task(p, src_rq);
dec_nr_running(p, src_rq);
set_task_cpu(p, this_cpu);
inc_nr_running(p, this_rq);
- enqueue_task(p, this_array);
- p->timestamp = (p->timestamp - src_rq->most_recent_timestamp)
- + this_rq->most_recent_timestamp;
+
/*
- * Note that idle threads have a prio of MAX_PRIO, for this test
- * to be always true for them.
+ * If this task has already been running on src_rq this priority
+ * cycle, make the new runqueue think it has been on its cycle
*/
- if (TASK_PREEMPTS_CURR(p, this_rq))
- resched_task(this_rq->curr);
+ if (p->rotation == src_rq->prio_rotation)
+ p->rotation = this_rq->prio_rotation;
+ enqueue_task(p, this_rq);
+ p->timestamp = (p->timestamp - src_rq->most_recent_timestamp)
+ + this_rq->most_recent_timestamp;
+ try_preempt(p, this_rq);
}
/*
@@ -2193,7 +2121,16 @@ int can_migrate_task(struct task_struct
return 1;
}
-#define rq_best_prio(rq) min((rq)->curr->prio, (rq)->best_expired_prio)
+static inline int rq_best_prio(struct rq *rq)
+{
+ int best_prio, exp_prio;
+
+ best_prio = sched_find_first_bit(rq->dyn_bitmap);
+ exp_prio = find_next_bit(rq->exp_bitmap, MAX_PRIO, MAX_RT_PRIO);
+ if (unlikely(best_prio > exp_prio))
+ best_prio = exp_prio;
+ return best_prio;
+}
/*
* move_tasks tries to move up to max_nr_move tasks and max_load_move weighted
@@ -2209,7 +2146,7 @@ static int move_tasks(struct rq *this_rq
{
int idx, pulled = 0, pinned = 0, this_best_prio, best_prio,
best_prio_seen, skip_for_load;
- struct prio_array *array, *dst_array;
+ struct prio_array *array;
struct list_head *head, *curr;
struct task_struct *tmp;
long rem_load_move;
@@ -2236,31 +2173,28 @@ static int move_tasks(struct rq *this_rq
* be cache-cold, thus switching CPUs has the least effect
* on them.
*/
- if (busiest->expired->nr_active) {
- array = busiest->expired;
- dst_array = this_rq->expired;
- } else {
- array = busiest->active;
- dst_array = this_rq->active;
- }
-
+ array = busiest->expired;
new_array:
/* Start searching at priority 0: */
idx = 0;
skip_bitmap:
if (!idx)
- idx = sched_find_first_bit(array->bitmap);
+ idx = sched_find_first_bit(array->prio_bitmap);
else
- idx = find_next_bit(array->bitmap, MAX_PRIO, idx);
+ idx = find_next_bit(array->prio_bitmap, MAX_PRIO, idx);
if (idx >= MAX_PRIO) {
- if (array == busiest->expired && busiest->active->nr_active) {
+ if (array == busiest->expired) {
array = busiest->active;
- dst_array = this_rq->active;
goto new_array;
}
goto out;
}
+ if (unlikely(list_empty(array->queue + idx))) {
+ __clear_bit(idx, array->prio_bitmap);
+ goto skip_bitmap;
+ }
+
head = array->queue + idx;
curr = head->prev;
skip_queue:
@@ -2286,7 +2220,7 @@ skip_queue:
goto skip_bitmap;
}
- pull_task(busiest, array, tmp, this_rq, dst_array, this_cpu);
+ pull_task(busiest, array, tmp, this_rq, this_cpu);
pulled++;
rem_load_move -= tmp->load_weight;
@@ -3268,27 +3202,6 @@ unsigned long long current_sched_time(co
}
/*
- * We place interactive tasks back into the active array, if possible.
- *
- * To guarantee that this does not starve expired tasks we ignore the
- * interactivity of a task if the first expired task had to wait more
- * than a 'reasonable' amount of time. This deadline timeout is
- * load-dependent, as the frequency of array switched decreases with
- * increasing number of running tasks. We also ignore the interactivity
- * if a better static_prio task has expired:
- */
-static inline int expired_starving(struct rq *rq)
-{
- if (rq->curr->static_prio > rq->best_expired_prio)
- return 1;
- if (!STARVATION_LIMIT || !rq->expired_timestamp)
- return 0;
- if (jiffies - rq->expired_timestamp > STARVATION_LIMIT * rq->nr_running)
- return 1;
- return 0;
-}
-
-/*
* Account user cpu time to a process.
* @p: the process that the cpu time gets accounted to
* @hardirq_offset: the offset to subtract from hardirq_count()
@@ -3361,87 +3274,143 @@ void account_steal_time(struct task_stru
cpustat->steal = cputime64_add(cpustat->steal, tmp);
}
+/*
+ * The task has used up its quota of running in this prio_level so it must be
+ * dropped a priority level, all managed by recalc_task_prio().
+ */
+static void task_expired_entitlement(struct rq *rq, struct task_struct *p)
+{
+ struct prio_array *old_array;
+ int old_prio;
+
+ set_tsk_need_resched(p);
+ if (unlikely(p->first_time_slice))
+ p->first_time_slice = 0;
+ if (rt_task(p)) {
+ p->time_slice = p->quota;
+ return;
+ }
+ old_array = p->array;
+ old_prio = p->prio;
+ /* p->prio and p->array will be updated in recalc_task_prio */
+ recalc_task_prio(p, rq);
+ requeue_task(p, rq, old_array, old_prio);
+}
+
+/*
+ * A major priority rotation occurs when all priority quotas for this array
+ * have been exhausted.
+ */
+static inline void major_prio_rotation(struct rq *rq)
+{
+ struct prio_array *new_array = rq->expired;
+
+ rq->expired = rq->active;
+ rq->active = new_array;
+ rq->exp_bitmap = rq->expired->prio_bitmap;
+ rq->dyn_bitmap = rq->active->prio_bitmap;
+ rq->prio_rotation++;
+}
+
+/*
+ * This is the heart of the virtual deadline priority management.
+ *
+ * We have used up the quota allocated to this priority level so we rotate
+ * the prio_level of the runqueue to the next lowest priority. We merge any
+ * remaining tasks at this level current_queue with the next priority and
+ * reset this level's queue. MAX_PRIO - 1 is a special case where we perform
+ * a major rotation.
+ */
+static inline void rotate_runqueue_priority(struct rq *rq)
+{
+ int new_prio_level;
+ struct prio_array *array;
+
+ /*
+ * Make sure we don't have tasks still on the active array that
+ * haven't run due to not preempting a lower priority task. This can
+ * happen on list merging or smp balancing.
+ */
+ if (unlikely(sched_find_first_bit(rq->dyn_bitmap) < rq->prio_level))
+ return;
+
+ array = rq->active;
+ if (rq->prio_level > MAX_PRIO - 2) {
+ /* Major rotation required */
+ struct prio_array *new_queue = rq->expired;
+
+ /*
+ * On a major rotation we move everything remaining to best
+ * priority on the new array. The priority matrix bitmap will
+ * ensure tasks only get the slots each static priority
+ * deserves.
+ */
+ new_prio_level = MAX_RT_PRIO;
+ if (!list_empty(array->queue + rq->prio_level)) {
+ list_splice_tail_init(array->queue + rq->prio_level,
+ new_queue->queue + new_prio_level);
+ }
+ memset(rq->prio_quota, 0, ARRAY_SIZE(rq->prio_quota));
+ major_prio_rotation(rq);
+ } else {
+ /* Minor rotation */
+ new_prio_level = rq->prio_level + 1;
+ __clear_bit(rq->prio_level, rq->dyn_bitmap);
+ if (!list_empty(array->queue + rq->prio_level)) {
+ list_splice_tail_init(array->queue + rq->prio_level,
+ array->queue + new_prio_level);
+ __set_bit(new_prio_level, rq->dyn_bitmap);
+ }
+ rq_quota(rq, rq->prio_level) = 0;
+ }
+ rq->prio_level = new_prio_level;
+ /*
+ * As we are merging to a prio_level that may not have anything in
+ * its quota we add 1 to ensure the tasks get to run in schedule() to
+ * add their quota to it.
+ */
+ rq_quota(rq, new_prio_level) += 1;
+}
+
static void task_running_tick(struct rq *rq, struct task_struct *p)
{
- if (p->array != rq->active) {
+ if (unlikely(!task_queued(p))) {
/* Task has expired but was not scheduled yet */
set_tsk_need_resched(p);
return;
}
+ /* SCHED_FIFO tasks never run out of timeslice. */
+ if (unlikely(p->policy == SCHED_FIFO))
+ return;
+
spin_lock(&rq->lock);
/*
- * The task was running during this tick - update the
- * time slice counter. Note: we do not update a thread's
- * priority until it either goes to sleep or uses up its
- * timeslice. This makes it possible for interactive tasks
- * to use up their timeslices at their highest priority levels.
+ * Accounting is performed by both the task and the runqueue. This
+ * allows frequently sleeping tasks to get their proper quota of
+ * cpu as the runqueue will have their quota still available at
+ * the appropriate priority level. It also means frequently waking
+ * tasks that might miss the scheduler_tick() will get forced down
+ * priority regardless.
+ */
+ if (!--p->time_slice)
+ task_expired_entitlement(rq, p);
+ /*
+ * We only employ the deadline mechanism if we run over the quota.
+ * It allows aliasing problems around the scheduler_tick to be
+ * less harmful.
*/
- if (rt_task(p)) {
- /*
- * RR tasks need a special form of timeslice management.
- * FIFO tasks have no timeslices.
- */
- if ((p->policy == SCHED_RR) && !--p->time_slice) {
- p->time_slice = task_timeslice(p);
+ if (!rt_task(p) && --rq_quota(rq, rq->prio_level) < 0) {
+ if (unlikely(p->first_time_slice))
p->first_time_slice = 0;
- set_tsk_need_resched(p);
-
- /* put it at the end of the queue: */
- requeue_task(p, rq->active);
- }
- goto out_unlock;
- }
- if (!--p->time_slice) {
- dequeue_task(p, rq->active);
+ rotate_runqueue_priority(rq);
set_tsk_need_resched(p);
- p->prio = effective_prio(p);
- p->time_slice = task_timeslice(p);
- p->first_time_slice = 0;
-
- if (!rq->expired_timestamp)
- rq->expired_timestamp = jiffies;
- if (!TASK_INTERACTIVE(p) || expired_starving(rq)) {
- enqueue_task(p, rq->expired);
- if (p->static_prio < rq->best_expired_prio)
- rq->best_expired_prio = p->static_prio;
- } else
- enqueue_task(p, rq->active);
- } else {
- /*
- * Prevent a too long timeslice allowing a task to monopolize
- * the CPU. We do this by splitting up the timeslice into
- * smaller pieces.
- *
- * Note: this does not mean the task's timeslices expire or
- * get lost in any way, they just might be preempted by
- * another task of equal priority. (one with higher
- * priority would have preempted this task already.) We
- * requeue this task to the end of the list on this priority
- * level, which is in essence a round-robin of tasks with
- * equal priority.
- *
- * This only applies to tasks in the interactive
- * delta range with at least TIMESLICE_GRANULARITY to requeue.
- */
- if (TASK_INTERACTIVE(p) && !((task_timeslice(p) -
- p->time_slice) % TIMESLICE_GRANULARITY(p)) &&
- (p->time_slice >= TIMESLICE_GRANULARITY(p)) &&
- (p->array == rq->active)) {
-
- requeue_task(p, rq->active);
- set_tsk_need_resched(p);
- }
}
-out_unlock:
spin_unlock(&rq->lock);
}
/*
* This function gets called by the timer code, with HZ frequency.
* We call it with interrupts disabled.
- *
- * It also gets called by the fork code, when changing the parent's
- * timeslices.
*/
void scheduler_tick(void)
{
@@ -3500,10 +3469,88 @@ EXPORT_SYMBOL(sub_preempt_count);
#endif
-static inline int interactive_sleep(enum sleep_type sleep_type)
+/* Is a dynamic_prio part of the allocated slots for this static_prio */
+static inline int entitled_slot(int static_prio, int dynamic_prio)
+{
+ return !test_bit(USER_PRIO(dynamic_prio),
+ prio_matrix[USER_PRIO(static_prio)]);
+}
+
+/*
+ * If a task is queued at a priority that isn't from its bitmap we exchange
+ * by setting one of the entitlement bits.
+ */
+static inline void exchange_slot(struct task_struct *p, int prio)
{
- return (sleep_type == SLEEP_INTERACTIVE ||
- sleep_type == SLEEP_INTERRUPTED);
+ int slot = next_prio_slot(p, prio);
+
+ if (slot < MAX_PRIO)
+ __set_bit(USER_PRIO(slot), p->bitmap);
+}
+
+/*
+ * next_dynamic_task finds the next suitable dynamic task. As the dyn_bitmap
+ * contains all the active and expired dynamic tasks sequentially we only
+ * need to do one bitmap lookup.
+ */
+static inline struct task_struct *next_dynamic_task(struct rq *rq, int idx)
+{
+ struct task_struct *next;
+ struct list_head *queue;
+ struct prio_array *array = rq->active;
+ int expirations = 0;
+
+retry:
+ if (idx >= MAX_PRIO) {
+ BUG_ON(++expirations > 1);
+ /*
+ * We have selected a bit from the expired range so there are
+ * no more tasks in the active array.
+ */
+ major_prio_rotation(rq);
+ array = rq->active;
+ idx = find_next_bit(rq->dyn_bitmap, MAX_PRIO, MAX_RT_PRIO);
+ }
+ if (unlikely(list_empty(array->queue + idx))) {
+ /*
+ * This can happen because they are not always cleared on
+ * dequeue_task since they may have been dequeued while
+ * waiting on a runqueue and a rotation has occurred in the
+ * interim. A very rare occurrence.
+ */
+ __clear_bit(idx, rq->dyn_bitmap);
+ idx = find_next_bit(rq->dyn_bitmap, MAX_PRIO, idx + 1);
+ goto retry;
+ }
+ queue = array->queue + idx;
+ next = list_entry(queue->next, struct task_struct, run_list);
+ /*
+ * When the task is chosen it is checked to see if its quota has been
+ * added to this runqueue level which is only performed once per
+ * level per major rotation for each running task.
+ */
+ if (next->rotation != rq->prio_rotation) {
+ /* Task has moved during major rotation */
+ task_new_array(next, rq);
+ if (!entitled_slot(next->static_prio, idx))
+ exchange_slot(next, idx);
+ set_task_entitlement(next);
+ rq_quota(rq, idx) += next->quota;
+ } else if (!test_bit(USER_PRIO(idx), next->bitmap)) {
+ /* Task has moved during minor rotation */
+ if (!entitled_slot(next->static_prio, idx))
+ exchange_slot(next, idx);
+ set_task_entitlement(next);
+ rq_quota(rq, idx) += next->quota;
+ }
+ rq->prio_level = idx;
+ /*
+ * next needs to have its prio and array reset here in case the
+ * values are wrong due to priority rotation.
+ */
+ next->prio = idx;
+ next->array = array;
+ return next;
}
/*
@@ -3512,13 +3559,11 @@ static inline int interactive_sleep(enum
asmlinkage void __sched schedule(void)
{
struct task_struct *prev, *next;
- struct prio_array *array;
struct list_head *queue;
unsigned long long now;
- unsigned long run_time;
- int cpu, idx, new_prio;
long *switch_count;
struct rq *rq;
+ int cpu, idx;
/*
* Test if we are atomic. Since do_exit() needs to call into
@@ -3554,18 +3599,6 @@ need_resched_nonpreemptible:
schedstat_inc(rq, sched_cnt);
now = sched_clock();
- if (likely((long long)(now - prev->timestamp) < NS_MAX_SLEEP_AVG)) {
- run_time = now - prev->timestamp;
- if (unlikely((long long)(now - prev->timestamp) < 0))
- run_time = 0;
- } else
- run_time = NS_MAX_SLEEP_AVG;
-
- /*
- * Tasks charged proportionately less run_time at high sleep_avg to
- * delay them losing their interactive status
- */
- run_time /= (CURRENT_BONUS(prev) ? : 1);
spin_lock_irq(&rq->lock);
@@ -3587,46 +3620,17 @@ need_resched_nonpreemptible:
idle_balance(cpu, rq);
if (!rq->nr_running) {
next = rq->idle;
- rq->expired_timestamp = 0;
goto switch_tasks;
}
}
- array = rq->active;
- if (unlikely(!array->nr_active)) {
- /*
- * Switch the active and expired arrays.
- */
- schedstat_inc(rq, sched_switch);
- rq->active = rq->expired;
- rq->expired = array;
- array = rq->active;
- rq->expired_timestamp = 0;
- rq->best_expired_prio = MAX_PRIO;
+ idx = sched_find_first_bit(rq->dyn_bitmap);
+ if (!rt_prio(idx))
+ next = next_dynamic_task(rq, idx);
+ else {
+ queue = rq->active->queue + idx;
+ next = list_entry(queue->next, struct task_struct, run_list);
}
-
- idx = sched_find_first_bit(array->bitmap);
- queue = array->queue + idx;
- next = list_entry(queue->next, struct task_struct, run_list);
-
- if (!rt_task(next) && interactive_sleep(next->sleep_type)) {
- unsigned long long delta = now - next->timestamp;
- if (unlikely((long long)(now - next->timestamp) < 0))
- delta = 0;
-
- if (next->sleep_type == SLEEP_INTERACTIVE)
- delta = delta * (ON_RUNQUEUE_WEIGHT * 128 / 100) / 128;
-
- array = next->array;
- new_prio = recalc_task_prio(next, next->timestamp + delta);
-
- if (unlikely(next->prio != new_prio)) {
- dequeue_task(next, array);
- next->prio = new_prio;
- enqueue_task(next, array);
- }
- }
- next->sleep_type = SLEEP_NORMAL;
switch_tasks:
if (next == rq->idle)
schedstat_inc(rq, sched_goidle);
@@ -3636,10 +3640,6 @@ switch_tasks:
rcu_qsctr_inc(task_cpu(prev));
update_cpu_clock(prev, rq, now);
-
- prev->sleep_avg -= run_time;
- if ((long)prev->sleep_avg <= 0)
- prev->sleep_avg = 0;
prev->timestamp = prev->last_ran = now;
sched_info_switch(prev, next);
@@ -4075,29 +4075,21 @@ EXPORT_SYMBOL(sleep_on_timeout);
*/
void rt_mutex_setprio(struct task_struct *p, int prio)
{
- struct prio_array *array;
unsigned long flags;
+ int queued, oldprio;
struct rq *rq;
- int oldprio;
BUG_ON(prio < 0 || prio > MAX_PRIO);
rq = task_rq_lock(p, &flags);
oldprio = p->prio;
- array = p->array;
- if (array)
- dequeue_task(p, array);
+ if ((queued = task_queued(p)))
+ dequeue_task(p, rq);
p->prio = prio;
- if (array) {
- /*
- * If changing to an RT priority then queue it
- * in the active array!
- */
- if (rt_task(p))
- array = rq->active;
- enqueue_task(p, array);
+ if (queued) {
+ enqueue_task(p, rq);
/*
* Reschedule if we are currently running on this runqueue and
* our priority decreased, or if we are not currently running on
@@ -4106,8 +4098,8 @@ void rt_mutex_setprio(struct task_struct
if (task_running(rq, p)) {
if (p->prio > oldprio)
resched_task(rq->curr);
- } else if (TASK_PREEMPTS_CURR(p, rq))
- resched_task(rq->curr);
+ } else
+ try_preempt(p, rq);
}
task_rq_unlock(rq, &flags);
}
@@ -4116,8 +4108,7 @@ void rt_mutex_setprio(struct task_struct
void set_user_nice(struct task_struct *p, long nice)
{
- struct prio_array *array;
- int old_prio, delta;
+ int queued, old_prio,delta;
unsigned long flags;
struct rq *rq;
@@ -4138,9 +4129,8 @@ void set_user_nice(struct task_struct *p
p->static_prio = NICE_TO_PRIO(nice);
goto out_unlock;
}
- array = p->array;
- if (array) {
- dequeue_task(p, array);
+ if ((queued = task_queued(p))) {
+ dequeue_task(p, rq);
dec_raw_weighted_load(rq, p);
}
@@ -4150,8 +4140,8 @@ void set_user_nice(struct task_struct *p
p->prio = effective_prio(p);
delta = p->prio - old_prio;
- if (array) {
- enqueue_task(p, array);
+ if (queued) {
+ enqueue_task(p, rq);
inc_raw_weighted_load(rq, p);
/*
* If the task increased its priority or is running and
@@ -4161,6 +4151,7 @@ void set_user_nice(struct task_struct *p
resched_task(rq->curr);
}
out_unlock:
+ p->quota = rr_quota(p);
task_rq_unlock(rq, &flags);
}
EXPORT_SYMBOL(set_user_nice);
@@ -4227,7 +4218,7 @@ asmlinkage long sys_nice(int increment)
*
* This is the priority value as seen by users in /proc.
* RT tasks are offset by -200. Normal tasks are centered
- * around 0, value goes from -16 to +15.
+ * around 0, value goes from 0 to +19.
*/
int task_prio(const struct task_struct *p)
{
@@ -4274,18 +4265,13 @@ static inline struct task_struct *find_p
/* Actually do priority change: must hold rq lock. */
static void __setscheduler(struct task_struct *p, int policy, int prio)
{
- BUG_ON(p->array);
+ BUG_ON(task_queued(p));
p->policy = policy;
p->rt_priority = prio;
p->normal_prio = normal_prio(p);
/* we are holding p->pi_lock already */
p->prio = rt_mutex_getprio(p);
- /*
- * SCHED_BATCH tasks are treated as perpetual CPU hogs:
- */
- if (policy == SCHED_BATCH)
- p->sleep_avg = 0;
set_load_weight(p);
}
@@ -4300,8 +4286,7 @@ static void __setscheduler(struct task_s
int sched_setscheduler(struct task_struct *p, int policy,
struct sched_param *param)
{
- int retval, oldprio, oldpolicy = -1;
- struct prio_array *array;
+ int queued, retval, oldprio, oldpolicy = -1;
unsigned long flags;
struct rq *rq;
@@ -4375,12 +4360,11 @@ recheck:
spin_unlock_irqrestore(&p->pi_lock, flags);
goto recheck;
}
- array = p->array;
- if (array)
+ if ((queued = task_queued(p)))
deactivate_task(p, rq);
oldprio = p->prio;
__setscheduler(p, policy, param->sched_priority);
- if (array) {
+ if (queued) {
__activate_task(p, rq);
/*
* Reschedule if we are currently running on this runqueue and
@@ -4390,8 +4374,8 @@ recheck:
if (task_running(rq, p)) {
if (p->prio > oldprio)
resched_task(rq->curr);
- } else if (TASK_PREEMPTS_CURR(p, rq))
- resched_task(rq->curr);
+ } else
+ try_preempt(p, rq);
}
__task_rq_unlock(rq);
spin_unlock_irqrestore(&p->pi_lock, flags);
@@ -4664,40 +4648,19 @@ asmlinkage long sys_sched_getaffinity(pi
* sys_sched_yield - yield the current processor to other threads.
*
* This function yields the current CPU by moving the calling thread
- * to the expired array. If there are no other threads running on this
- * CPU then this function will return.
+ * to the end of its current priority queue. If there are no other
+ * threads running on this cpu this function will return.
*/
asmlinkage long sys_sched_yield(void)
{
struct rq *rq = this_rq_lock();
- struct prio_array *array = current->array, *target = rq->expired;
+ struct task_struct *p = current;
schedstat_inc(rq, yld_cnt);
- /*
- * We implement yielding by moving the task into the expired
- * queue.
- *
- * (special rule: RT tasks will just roundrobin in the active
- * array.)
- */
- if (rt_task(current))
- target = rq->active;
-
- if (array->nr_active == 1) {
- schedstat_inc(rq, yld_act_empty);
- if (!rq->expired->nr_active)
- schedstat_inc(rq, yld_both_empty);
- } else if (!rq->expired->nr_active)
- schedstat_inc(rq, yld_exp_empty);
-
- if (array != target) {
- dequeue_task(current, array);
- enqueue_task(current, target);
- } else
- /*
- * requeue_task is cheaper so perform that if possible.
- */
- requeue_task(current, array);
+ if (rq->nr_running == 1)
+ schedstat_inc(rq, yld_both_empty);
+ else
+ list_move_tail(&p->run_list, p->array->queue + p->prio);
/*
* Since we are going to call schedule() anyway, there's
@@ -5036,10 +4999,10 @@ void __cpuinit init_idle(struct task_str
struct rq *rq = cpu_rq(cpu);
unsigned long flags;
+ bitmap_zero(idle->bitmap, PRIO_RANGE + 1);
idle->timestamp = sched_clock();
- idle->sleep_avg = 0;
idle->array = NULL;
- idle->prio = idle->normal_prio = MAX_PRIO;
+ idle->prio = idle->normal_prio = NICE_TO_PRIO(0);
idle->state = TASK_RUNNING;
idle->cpus_allowed = cpumask_of_cpu(cpu);
set_task_cpu(idle, cpu);
@@ -5158,7 +5121,7 @@ static int __migrate_task(struct task_st
goto out;
set_task_cpu(p, dest_cpu);
- if (p->array) {
+ if (task_queued(p)) {
/*
* Sync timestamp with rq_dest's before activating.
* The same thing could be achieved by doing this step
@@ -5169,8 +5132,7 @@ static int __migrate_task(struct task_st
+ rq_dest->most_recent_timestamp;
deactivate_task(p, rq_src);
__activate_task(p, rq_dest);
- if (TASK_PREEMPTS_CURR(p, rq_dest))
- resched_task(rq_dest->curr);
+ try_preempt(p, rq_dest);
}
ret = 1;
out:
@@ -5575,7 +5537,7 @@ migration_call(struct notifier_block *nf
/* Idle task back to normal (off runqueue, low prio) */
rq = task_rq_lock(rq->idle, &flags);
deactivate_task(rq->idle, rq);
- rq->idle->static_prio = MAX_PRIO;
+ rq->idle->static_prio = NICE_TO_PRIO(0);
__setscheduler(rq->idle, SCHED_NORMAL, 0);
migrate_dead_tasks(cpu);
task_rq_unlock(rq, &flags);
@@ -7091,6 +7053,26 @@ void __init sched_init(void)
{
int i, j, k;
int highest_cpu = 0;
+ unsigned int rr_us = 0, rr_inc = RR_INTERVAL * 1000;
+
+ /* Generate the priority matrix */
+ for (i = 0; i < PRIO_RANGE; i++) {
+ if (i < 20) {
+ bitmap_zero(prio_matrix[i] , PRIO_RANGE);
+ j = PRIO_RANGE * PRIO_RANGE / (i + 1);
+ for (k = j; k < PRIO_RANGE * PRIO_RANGE; k += j)
+ __set_bit(k / PRIO_RANGE, prio_matrix[i]);
+ } else if (i == 20) {
+ bitmap_fill(prio_matrix[i], PRIO_RANGE);
+ for (k = 1; k < PRIO_RANGE; k += 2)
+ __clear_bit(k, prio_matrix[i]);
+ } else {
+ bitmap_fill(prio_matrix[i], PRIO_RANGE);
+ j = PRIO_RANGE * PRIO_RANGE / (PRIO_RANGE - i + 1);
+ for (k = j; k < PRIO_RANGE * PRIO_RANGE; k += j)
+ __clear_bit(k / PRIO_RANGE, prio_matrix[i]);
+ }
+ }
for_each_possible_cpu(i) {
struct prio_array *array;
@@ -7100,9 +7082,12 @@ void __init sched_init(void)
spin_lock_init(&rq->lock);
lockdep_set_class(&rq->lock, &rq->rq_lock_key);
rq->nr_running = 0;
+ rq->prio_rotation = 0;
+ rq->prio_level = MAX_RT_PRIO;
rq->active = rq->arrays;
rq->expired = rq->arrays + 1;
- rq->best_expired_prio = MAX_PRIO;
+ rq->dyn_bitmap = rq->active->prio_bitmap;
+ rq->exp_bitmap = rq->expired->prio_bitmap;
#ifdef CONFIG_SMP
rq->sd = NULL;
@@ -7117,16 +7102,23 @@ void __init sched_init(void)
atomic_set(&rq->nr_iowait, 0);
for (j = 0; j < 2; j++) {
+
array = rq->arrays + j;
- for (k = 0; k < MAX_PRIO; k++) {
+ for (k = 0; k < MAX_PRIO; k++)
INIT_LIST_HEAD(array->queue + k);
- __clear_bit(k, array->bitmap);
- }
- // delimiter for bitsearch
- __set_bit(MAX_PRIO, array->bitmap);
+ bitmap_zero(array->prio_bitmap, MAX_PRIO);
+ /* delimiter for bitsearch */
+ __set_bit(MAX_PRIO, array->prio_bitmap);
}
+ for (k = 0; k < PRIO_RANGE; k++)
+ rq->prio_quota[k] = 0;
highest_cpu = i;
+
+ /* Every added cpu increases the rr_interval */
+ rr_us += rr_inc;
+ rr_inc /= 2;
}
+ rr_interval = rr_us / 1000 ? : 1;
set_load_weight(&init_task);
@@ -7182,10 +7174,10 @@ EXPORT_SYMBOL(__might_sleep);
#ifdef CONFIG_MAGIC_SYSRQ
void normalize_rt_tasks(void)
{
- struct prio_array *array;
struct task_struct *p;
unsigned long flags;
struct rq *rq;
+ int queued;
read_lock_irq(&tasklist_lock);
for_each_process(p) {
@@ -7195,11 +7187,10 @@ void normalize_rt_tasks(void)
spin_lock_irqsave(&p->pi_lock, flags);
rq = __task_rq_lock(p);
- array = p->array;
- if (array)
+ if ((queued = task_queued(p)))
deactivate_task(p, task_rq(p));
__setscheduler(p, SCHED_NORMAL, 0);
- if (array) {
+ if (queued) {
__activate_task(p, task_rq(p));
resched_task(rq->curr);
}
--
-ck
-
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