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Message-ID: <20070131150155.GA14145@in.ibm.com>
Date: Wed, 31 Jan 2007 20:31:55 +0530
From: Srivatsa Vaddagiri <vatsa@...ibm.com>
To: riel@...hat.com, Ingo Molnar <mingo@...e.hu>,
Nick Piggin <nickpiggin@...oo.com.au>,
Andrew Morton <akpm@...l.org>,
Eric Piel <Eric.Piel@...mplin-utc.net>,
Kirill Korotaev <dev@...ru>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] core scheduler changes
On Fri, Jan 26, 2007 at 11:33:17AM +0530, Srivatsa Vaddagiri wrote:
>
> This patch does several things:
>
> - Introduces the notion of control window (current set at 1
> sec - ideally the window size should be adjusted based on
> number of users to avoid rapid context switches). Bandwidth of each
> user is controlled within this window. rq->last_update tracks where
> are in the current window.
The patch below makes the control window size configurable (as a macro),
sets the default window size at 10 sec and also fixes a compile error (for
!CONFIG_FAIRSCHED case).
Ideally the window size needs to be determined at run time (based on number of
users). I will address that if there is sufficient interest on a patch
like this ..
Signed-off-by : Srivatsa Vaddagiri <vatsa@...ibm.com>
---
diff -puN kernel/sched.c~window-fix kernel/sched.c
--- linux-2.6.20-rc5/kernel/sched.c~window-fix 2007-01-31 19:59:48.000000000 +0530
+++ linux-2.6.20-rc5-vatsa/kernel/sched.c 2007-01-31 20:08:57.000000000 +0530
@@ -769,17 +769,24 @@ static inline int is_user_starving(struc
return 0;
}
-/* Are we past the 1-sec control window? If so, all groups get to renew their
+#define WINDOW_SIZE (10*HZ)
+
+/* Are we past the control window? If so, all groups get to renew their
* expired tokens.
*/
-static inline void adjust_control_window(void)
+static inline void adjust_control_window(int force)
{
struct rq *rq = this_rq();
unsigned long delta;
+ if (force) {
+ rq->last_update = jiffies;
+ return;
+ }
+
delta = jiffies - rq->last_update;
- if (delta >= HZ)
- rq->last_update += (delta/HZ) * HZ;
+ if (delta >= WINDOW_SIZE)
+ rq->last_update += (delta/WINDOW_SIZE) * WINDOW_SIZE;
}
/* Account group's cpu usage */
@@ -788,7 +795,7 @@ static inline void inc_cpu_usage(struct
struct user_struct *user = p->user;
struct cpu_usage *cu;
- adjust_control_window();
+ adjust_control_window(0);
if (!user->cpu_limit)
return;
@@ -803,7 +810,7 @@ static inline int task_over_cpu_limit(st
struct user_struct *user = p->user;
struct cpu_usage *cu;
- adjust_control_window();
+ adjust_control_window(0);
if (!user->cpu_limit)
return 0;
@@ -811,7 +818,7 @@ static inline int task_over_cpu_limit(st
cu = per_cpu_ptr(user->cpu_usage, task_cpu(p));
if (cu->last_update != rq->last_update) {
/* Replenish tokens */
- cu->tokens += user->cpu_limit * HZ / 100;
+ cu->tokens += user->cpu_limit * WINDOW_SIZE / 100;
cu->last_update = rq->last_update;
}
@@ -830,6 +837,7 @@ static int task_over_cpu_limit(struct ta
static void set_tsk_starving(struct task_struct *p) { }
static void clear_tsk_starving(struct task_struct *p) { }
static int is_user_starving(struct task_struct *p) { return 0;}
+static inline void adjust_control_window(int force) { }
#endif /* CONFIG_FAIRSCHED */
@@ -3668,7 +3676,7 @@ pick_next_task:
}
if (task_over_cpu_limit(next))
- rq->last_update = jiffies;
+ adjust_control_window(1);
if (!next->time_slice)
next->time_slice = task_timeslice(next);
clear_tsk_starving(next);
_
--
Regards,
vatsa
-
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