From: Matt Fleming <matt@codeblueprint.co.uk>
To: Yuyang Du <yuyang.du@intel.com>
Cc: peterz@infradead.org, mingo@kernel.org,
linux-kernel@vger.kernel.org, bsegall@google.com, pjt@google.com,
morten.rasmussen@arm.com, vincent.guittot@linaro.org,
dietmar.eggemann@arm.com
Subject: Re: [PATCH v4 3/5] sched/fair: Skip detach sched avgs for new task when changing task groups
Date: Mon, 6 Jun 2016 15:03:38 +0100 [thread overview]
Message-ID: <20160606140338.GS2658@codeblueprint.co.uk> (raw)
In-Reply-To: <1465172441-27727-4-git-send-email-yuyang.du@intel.com>
On Mon, 06 Jun, at 08:20:39AM, Yuyang Du wrote:
> Newly forked task has not been enqueued, so should not be removed from
> cfs_rq in task_move_group_fair(). To do so, we need to pass the fork
> information all the way from sched_move_task() to task_move_group_fair().
>
> Signed-off-by: Yuyang Du <yuyang.du@intel.com>
> ---
> kernel/sched/auto_group.c | 2 +-
> kernel/sched/core.c | 8 ++++----
> kernel/sched/fair.c | 8 ++++++--
> kernel/sched/sched.h | 4 ++--
> 4 files changed, 13 insertions(+), 9 deletions(-)
[...]
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 28b3415..370e284 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -8429,9 +8429,13 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
> }
>
> #ifdef CONFIG_FAIR_GROUP_SCHED
> -static void task_move_group_fair(struct task_struct *p)
> +static void task_move_group_fair(struct task_struct *p, bool fork)
> {
> - detach_task_cfs_rq(p);
> + /*
> + * Newly forked task should not be removed from any cfs_rq
> + */
> + if (!fork)
> + detach_task_cfs_rq(p);
> set_task_rq(p, task_cpu(p));
> attach_task_cfs_rq(p);
> /*
Wouldn't it be more symmetric to add,
if (p->se.avg.last_update_time)
__update_load_avg(...)
to detach_entity_load_avg() so that there's no need to pass the @fork
parameter all the way down the stack, and more importantly, remember
to *not* call detach_task_cfs_rq() if the code changes in the future?
Additionally adding the above check looks like it would fix a race
that (I think) occurs if a newly forked task's class is changed before
it is enqueued in wake_up_new_task().
next prev parent reply other threads:[~2016-06-06 14:03 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-06 0:20 [PATCH v4 0/5] sched/fair: Fix attach and detach sched avgs for task group change or sched class change Yuyang Du
2016-06-06 0:20 ` [PATCH v4 1/5] sched/fair: Clean up attach_entity_load_avg() Yuyang Du
2016-06-06 13:30 ` Matt Fleming
2016-06-06 13:40 ` Vincent Guittot
2016-06-06 14:06 ` Matt Fleming
2016-06-06 14:27 ` Peter Zijlstra
2016-06-06 0:20 ` [PATCH v4 2/5] sched/fair: Fix attaching task sched avgs twice when switching to fair or changing task group Yuyang Du
2016-06-06 9:54 ` Peter Zijlstra
2016-06-06 19:38 ` Yuyang Du
2016-06-06 12:32 ` Vincent Guittot
2016-06-06 19:05 ` Yuyang Du
2016-06-07 8:09 ` Vincent Guittot
2016-06-07 18:16 ` Yuyang Du
2016-06-06 0:20 ` [PATCH v4 3/5] sched/fair: Skip detach sched avgs for new task when changing task groups Yuyang Du
2016-06-06 9:58 ` Peter Zijlstra
2016-06-06 14:03 ` Matt Fleming [this message]
2016-06-06 19:15 ` Yuyang Du
2016-06-06 0:20 ` [PATCH v4 4/5] sched/fair: Move load and util avgs from wake_up_new_task() to sched_fork() Yuyang Du
2016-06-06 0:20 ` [PATCH v4 5/5] sched/fair: Add inline to detach_entity_load_evg() Yuyang Du
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