From: Mike Galbraith <efault@gmx.de>
To: Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@osdl.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
Peter Williams <pwil3058@bigpond.net.au>,
Nick Piggin <nickpiggin@yahoo.com.au>,
Con Kolivas <kernel@kolivas.org>
Subject: Re: [patch 2.6.16-mm2 1/9] sched throttle tree extract - ignore invalid timestamps
Date: Sat, 01 Apr 2006 10:33:17 +0200 [thread overview]
Message-ID: <1143880397.7617.10.camel@homer> (raw)
In-Reply-To: <1143880124.7617.5.camel@homer>
On an SMP system, a task can awaken on a different cpu from where it
went to sleep. Timestamp inaccuracies can result from the attempt to
compensate for clock drift. Ignore resulting timewarps.
Signed-off-by: Mike Galbraith <efault@gmx.de>
--- linux-2.6.16-mm2/kernel/sched.c-0.fix_rt 2006-03-23 15:01:41.000000000 +0100
+++ linux-2.6.16-mm2/kernel/sched.c 2006-03-23 15:02:25.000000000 +0100
@@ -845,6 +845,15 @@ static int recalc_task_prio(task_t *p, u
unsigned long long __sleep_time = now - p->timestamp;
unsigned long sleep_time;
+ /*
+ * On SMP systems, a task can go to sleep on one CPU
+ * and wake up on another. When this happens, now can
+ * end up being less than p->timestamp for short sleeps.
+ * Ignore these, they're insignificant.
+ */
+ if (unlikely(now < p->timestamp))
+ __sleep_time = 0;
+
if (batch_task(p))
sleep_time = 0;
else {
next prev parent reply other threads:[~2006-04-01 8:32 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-01 8:28 [patch 2.6.16-mm2 0/9] sched throttle tree extract Mike Galbraith
2006-04-01 8:33 ` Mike Galbraith [this message]
2006-04-01 8:38 ` [patch 2.6.16-mm2 2/9] sched throttle tree extract - fix potential task uninterruptible bug Mike Galbraith
2006-04-01 8:44 ` [patch 2.6.16-mm2 3/9] sched throttle tree extract - remove IO priority barrier Mike Galbraith
2006-04-01 8:51 ` [patch 2.6.16-mm2 4/9] sched throttle tree extract - remove kthread barrier Mike Galbraith
2006-04-01 8:59 ` [patch 2.6.16-mm2 5/9] sched throttle tree extract - correct idle sleep logic Mike Galbraith
2006-04-01 9:12 ` [patch 2.6.16-mm2 6/9] sched throttle tree extract - move division to slow path Mike Galbraith
2006-04-01 9:23 ` [patch 2.6.16-mm2 7/9] sched throttle tree extract - implement throttling Mike Galbraith
2006-04-01 9:26 ` [patch 2.6.16-mm2 8/9] sched throttle tree extract - maximize timeslice accounting Mike Galbraith
2006-04-01 9:31 ` [patch 2.6.16-mm2 9/9] sched throttle tree extract - export tunables Mike Galbraith
2006-04-05 17:38 ` [patch 2.6.16-mm2 10/9] sched throttle tree extract - kill interactive task feedback loop Mike Galbraith
2006-04-05 23:15 ` Con Kolivas
2006-04-06 4:10 ` Mike Galbraith
2006-04-06 4:29 ` Con Kolivas
2006-04-01 16:53 ` [patch 2.6.16-mm2 5/9] sched throttle tree extract - correct idle sleep logic Lee Revell
2006-04-01 18:00 ` Mike Galbraith
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