From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> To: LKML <linux-kernel@vger.kernel.org>, cgroups <cgroups@vger.kernel.org> Cc: Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Paul Turner <pjt@google.com>, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Subject: [PATCH 1/3] sched: fix cgroup movement of newly created process Date: Thu, 15 Dec 2011 14:36:07 +0900 [thread overview] Message-ID: <20111215143607.2ee12c5d.nishimura@mxp.nes.nec.co.jp> (raw) In-Reply-To: <20111215143506.335e443e.nishimura@mxp.nes.nec.co.jp> There is a small race between do_fork() and sched_move_task(), which is trying to move the child. do_fork() sched_move_task() --------------------------------+--------------------------------- copy_process() sched_fork() task_fork_fair() -> vruntime of the child is initialized based on that of the parent. -> we can see the child in "tasks" file now. task_rq_lock() task_move_group_fair() -> child.se.vruntime -= (old)cfs_rq->min_vruntime += (new)cfs_rq->min_vruntime task_rq_unlock() wake_up_new_task() ... enqueue_entity() child.se.vruntime += cfs_rq->min_vruntime As a result, vruntime of the child becomes far bigger than min_vruntime, if (new)cfs_rq->min_vruntime >> (old)cfs_rq->min_vruntime. This patch fixes this problem by just ignoring such process in task_move_group_fair(), because the vruntime has already been normalized in task_fork_fair(). Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> --- kernel/sched/fair.c | 13 +++++++++++++ 1 files changed, 13 insertions(+), 0 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a4d2b7a..43cadd0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5336,6 +5336,19 @@ static void task_move_group_fair(struct task_struct *p, int on_rq) * to another cgroup's rq. This does somewhat interfere with the * fair sleeper stuff for the first placement, but who cares. */ + /* + * When !on_rq, vruntime of the task has usually NOT been normalized. + * But there are some cases where it has already been normalized: + * + * - Moving a forked child which is waiting for being woken up by + * wake_up_new_task(). + * + * To prevent boost or penalty in the new cfs_rq caused by delta + * min_vruntime between the two cfs_rqs, we skip vruntime adjustment. + */ + if (!on_rq && !p->se.sum_exec_runtime) + on_rq = 1; + if (!on_rq) p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime; set_task_rq(p, task_cpu(p)); -- 1.7.1
WARNING: multiple messages have this Message-ID (diff)
From: Daisuke Nishimura <nishimura-YQH0OdQVrdy45+QrQBaojngSJqDPrsil@public.gmane.org> To: LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org> Cc: Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>, Peter Zijlstra <a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public.gmane.org>, Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Daisuke Nishimura <nishimura-YQH0OdQVrdy45+QrQBaojngSJqDPrsil@public.gmane.org> Subject: [PATCH 1/3] sched: fix cgroup movement of newly created process Date: Thu, 15 Dec 2011 14:36:07 +0900 [thread overview] Message-ID: <20111215143607.2ee12c5d.nishimura@mxp.nes.nec.co.jp> (raw) In-Reply-To: <20111215143506.335e443e.nishimura-YQH0OdQVrdy45+QrQBaojngSJqDPrsil@public.gmane.org> There is a small race between do_fork() and sched_move_task(), which is trying to move the child. do_fork() sched_move_task() --------------------------------+--------------------------------- copy_process() sched_fork() task_fork_fair() -> vruntime of the child is initialized based on that of the parent. -> we can see the child in "tasks" file now. task_rq_lock() task_move_group_fair() -> child.se.vruntime -= (old)cfs_rq->min_vruntime += (new)cfs_rq->min_vruntime task_rq_unlock() wake_up_new_task() ... enqueue_entity() child.se.vruntime += cfs_rq->min_vruntime As a result, vruntime of the child becomes far bigger than min_vruntime, if (new)cfs_rq->min_vruntime >> (old)cfs_rq->min_vruntime. This patch fixes this problem by just ignoring such process in task_move_group_fair(), because the vruntime has already been normalized in task_fork_fair(). Signed-off-by: Daisuke Nishimura <nishimura-YQH0OdQVrdy45+QrQBaojngSJqDPrsil@public.gmane.org> --- kernel/sched/fair.c | 13 +++++++++++++ 1 files changed, 13 insertions(+), 0 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a4d2b7a..43cadd0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5336,6 +5336,19 @@ static void task_move_group_fair(struct task_struct *p, int on_rq) * to another cgroup's rq. This does somewhat interfere with the * fair sleeper stuff for the first placement, but who cares. */ + /* + * When !on_rq, vruntime of the task has usually NOT been normalized. + * But there are some cases where it has already been normalized: + * + * - Moving a forked child which is waiting for being woken up by + * wake_up_new_task(). + * + * To prevent boost or penalty in the new cfs_rq caused by delta + * min_vruntime between the two cfs_rqs, we skip vruntime adjustment. + */ + if (!on_rq && !p->se.sum_exec_runtime) + on_rq = 1; + if (!on_rq) p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime; set_task_rq(p, task_cpu(p)); -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2011-12-15 5:43 UTC|newest] Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-12-13 6:57 [PATCH 0/3] sched: some fixes for vruntime calculation related to cgroup movement Daisuke Nishimura 2011-12-13 6:57 ` Daisuke Nishimura 2011-12-13 6:57 ` [PATCH 1/3] sched: fix cgroup movement of newly created process Daisuke Nishimura 2011-12-13 6:57 ` Daisuke Nishimura 2011-12-13 12:01 ` Paul Turner 2011-12-13 12:01 ` Paul Turner 2011-12-14 1:04 ` Daisuke Nishimura 2011-12-14 1:04 ` Daisuke Nishimura 2011-12-13 12:41 ` Peter Zijlstra 2011-12-13 12:41 ` Peter Zijlstra 2011-12-14 1:05 ` Daisuke Nishimura 2011-12-14 1:05 ` Daisuke Nishimura 2011-12-13 6:58 ` [PATCH 2/3] sched: fix cgroup movement of forking process Daisuke Nishimura 2011-12-13 6:58 ` Daisuke Nishimura 2011-12-13 12:22 ` Paul Turner 2011-12-13 12:22 ` Paul Turner 2011-12-13 6:59 ` [PATCH 3/3] sched: fix cgroup movement of waking process Daisuke Nishimura 2011-12-13 6:59 ` Daisuke Nishimura 2011-12-13 12:24 ` Paul Turner 2011-12-13 12:24 ` Paul Turner 2011-12-15 5:35 ` [PATCH -tip 0/3] sched: some fixes for vruntime calculation related to cgroup movement(v2) Daisuke Nishimura 2011-12-15 5:36 ` Daisuke Nishimura [this message] 2011-12-15 5:36 ` [PATCH 1/3] sched: fix cgroup movement of newly created process Daisuke Nishimura 2011-12-21 11:45 ` [tip:sched/core] sched: Fix " tip-bot for Daisuke Nishimura 2011-12-15 5:36 ` [PATCH 2/3] sched: fix cgroup movement of forking process Daisuke Nishimura 2011-12-15 5:36 ` Daisuke Nishimura 2011-12-21 11:44 ` [tip:sched/core] sched: Fix " tip-bot for Daisuke Nishimura 2011-12-21 17:26 ` Tejun Heo 2011-12-21 17:37 ` Tejun Heo 2011-12-22 1:54 ` Frederic Weisbecker 2011-12-22 2:01 ` Tejun Heo 2011-12-15 5:37 ` [PATCH 3/3] sched: fix cgroup movement of waking process Daisuke Nishimura 2011-12-21 11:45 ` [tip:sched/core] sched: Fix " tip-bot for Daisuke Nishimura 2011-12-19 2:55 ` [PATCH -tip 0/3] sched: some fixes for vruntime calculation related to cgroup movement(v2) Daisuke Nishimura 2011-12-19 2:55 ` Daisuke Nishimura
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