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Date: Fri, 28 Sep 2012 01:02:19 -0700
From: tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
torvalds@...ux-foundation.org, a.p.zijlstra@...llo.nl,
pjt@...gle.com, riel@...hat.com, akpm@...ux-foundation.org,
tglx@...utronix.de
Subject: [tip:sched/numa] sched/numa: Detect 'big' processes
Commit-ID: 1b9fc936e56d62dfbb12ab4651c0432e91c10e2a
Gitweb: http://git.kernel.org/tip/1b9fc936e56d62dfbb12ab4651c0432e91c10e2a
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Mon, 16 Jul 2012 13:08:54 +0200
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 27 Sep 2012 17:04:48 +0200
sched/numa: Detect 'big' processes
Detect 'big' processes for which the one home-node per process isn't
going to work as desired.
The current policy for such tasks is to ignore them entirely and put
the home-node back to -1 (no preference) so they'll behave as if none
of this NUMA home node awareness is there.
The current heuristic for determining if a task is 'big' is if its
consuming more than 1/2 a node's worth of cputime. We might want to
add a term here looking at the RSS of the process and compare this
against the available memory per node.
Since we now do multiple things from the task_work thing, we need to
extend the state to determine which of the things we're there for -- a
change in numa node, or a periodic poll of 'big'-ness.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Rik van Riel <riel@...hat.com>
Cc: Paul Turner <pjt@...gle.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Link: http://lkml.kernel.org/n/tip-nqczclvw4g9p0us0yezui7q5@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
include/linux/mm_types.h | 1 +
include/linux/sched.h | 4 +-
kernel/sched/core.c | 12 ++++--
kernel/sched/fair.c | 96 ++++++++++++++++++++++++++++++++++++++-------
4 files changed, 93 insertions(+), 20 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index f407966..930c006 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -405,6 +405,7 @@ struct mm_struct {
struct cpumask cpumask_allocation;
#endif
#ifdef CONFIG_SCHED_NUMA
+ unsigned int numa_big;
unsigned long numa_next_scan;
#endif
struct uprobes_state uprobes_state;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 63dde76..b8f7461 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1521,8 +1521,10 @@ struct task_struct {
#endif
#ifdef CONFIG_SCHED_NUMA
int node; /* task home node */
- int node_last; /* home node filter */
+ int node_curr, node_last; /* home node filter */
u64 node_stamp; /* migration stamp */
+ u64 numa_runtime_stamp;
+ u64 numa_walltime_stamp;
unsigned long numa_contrib;
#endif /* CONFIG_SCHED_NUMA */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index fda809d..6668b0d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1535,13 +1535,18 @@ static void __sched_fork(struct task_struct *p)
#endif
#ifdef CONFIG_SCHED_NUMA
- if (p->mm && atomic_read(&p->mm->mm_users) == 1)
+ if (p->mm && atomic_read(&p->mm->mm_users) == 1) {
+ p->mm->numa_big = 0;
p->mm->numa_next_scan = jiffies;
+ }
p->node = -1;
+ p->node_curr = -1;
p->node_last = -1;
p->node_stamp = 0ULL;
-#endif /* CONFIG_NUMA */
+ p->numa_runtime_stamp = 0;
+ p->numa_walltime_stamp = local_clock();
+#endif /* CONFIG_SCHED_NUMA */
}
/*
@@ -6024,8 +6029,7 @@ void sched_setnode(struct task_struct *p, int node)
if (running)
p->sched_class->put_prev_task(rq, p);
- p->node = node;
- p->node_last = node;
+ p->node = p->node_curr = p->node_last = node;
if (running)
p->sched_class->set_curr_task(rq);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a1560fc..7ea50ac 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -809,14 +809,73 @@ static void account_offnode_dequeue(struct rq *rq, struct task_struct *p)
unsigned int sysctl_sched_numa_task_period = 2500;
/*
+ * Determine if a process is 'big'.
+ *
+ * Currently only looks at CPU-time used, maybe we should also add an RSS
+ * heuristic.
+ */
+static bool task_numa_big(struct task_struct *p)
+{
+ struct sched_domain *sd;
+ struct task_struct *t;
+ u64 walltime = local_clock();
+ u64 runtime = 0;
+ int weight = 0;
+
+ rcu_read_lock();
+ t = p;
+ do {
+ if (t->sched_class == &fair_sched_class)
+ runtime += t->se.sum_exec_runtime;
+ } while ((t = next_thread(t)) != p);
+
+ sd = rcu_dereference(__raw_get_cpu_var(sd_node));
+ if (sd)
+ weight = sd->span_weight;
+ rcu_read_unlock();
+
+ runtime -= p->numa_runtime_stamp;
+ walltime -= p->numa_walltime_stamp;
+
+ p->numa_runtime_stamp += runtime;
+ p->numa_walltime_stamp += walltime;
+
+ /*
+ * We're 'big' when we burn more than half a node's worth
+ * of cputime.
+ */
+ return runtime > walltime * max(1, weight / 2);
+}
+
+static inline bool need_numa_migration(struct task_struct *p)
+{
+ /*
+ * We need to change our home-node, its been different for 2 samples.
+ * See the whole P(n)^2 story in task_tick_numa().
+ */
+ return p->node_curr == p->node_last && p->node != p->node_curr;
+}
+
+static void sched_setnode_process(struct task_struct *p, int node)
+{
+ struct task_struct *t = p;
+
+ rcu_read_lock();
+ do {
+ sched_setnode(t, node);
+ } while ((t = next_thread(t)) != p);
+ rcu_read_unlock();
+}
+
+/*
* The expensive part of numa migration is done from task_work context.
* Triggered from task_tick_numa().
*/
void task_numa_work(struct callback_head *work)
{
unsigned long migrate, next_scan, now = jiffies;
- struct task_struct *t, *p = current;
- int node = p->node_last;
+ struct task_struct *p = current;
+ int big;
WARN_ON_ONCE(p != container_of(work, struct task_struct, rcu));
@@ -842,14 +901,19 @@ void task_numa_work(struct callback_head *work)
if (cmpxchg(&p->mm->numa_next_scan, migrate, next_scan) != migrate)
return;
- rcu_read_lock();
- t = p;
- do {
- sched_setnode(t, node);
- } while ((t = next_thread(t)) != p);
- rcu_read_unlock();
-
- lazy_migrate_process(p->mm);
+ /*
+ * If this task is too big, we bail on NUMA placement for the process.
+ */
+ big = p->mm->numa_big = task_numa_big(p);
+ if (big || need_numa_migration(p)) {
+ int node = p->node_curr;
+
+ if (big)
+ node = -1;
+ sched_setnode_process(p, node);
+ if (node != -1)
+ lazy_migrate_process(p->mm);
+ }
}
/*
@@ -861,12 +925,12 @@ void task_numa_work(struct callback_head *work)
void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
u64 period, now;
- int node;
/*
* We don't care about NUMA placement if we don't have memory.
+ * We also bail on placement if we're too big.
*/
- if (!curr->mm)
+ if (!curr->mm || curr->mm->numa_big)
return;
/*
@@ -889,9 +953,12 @@ void task_tick_numa(struct rq *rq, struct task_struct *curr)
if (now - curr->node_stamp > period) {
curr->node_stamp = now;
- node = numa_node_id();
- if (curr->node_last == node && curr->node != node) {
+ curr->node_last = curr->node_curr;
+ curr->node_curr = numa_node_id();
+
+ if (need_numa_migration(curr) ||
+ !time_before(jiffies, curr->mm->numa_next_scan)) {
/*
* We can re-use curr->rcu because we checked curr->mm
* != NULL so release_task()->call_rcu() was not called
@@ -901,7 +968,6 @@ void task_tick_numa(struct rq *rq, struct task_struct *curr)
init_task_work(&curr->rcu, task_numa_work);
task_work_add(curr, &curr->rcu, true);
}
- curr->node_last = node;
}
}
#else
--
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