lkml.org 
[lkml]   [2013]   [May]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 09/10] sched: task_sched_runtime introduce micro optimization
On Mon, Apr 29, 2013 at 11:17:17PM -0400, kosaki.motohiro@gmail.com wrote:
> From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>
> rq lock in task_sched_runtime() is necessary for two reasons. 1)
> accessing se.sum_exec_runtime is inatomic on 32bit and 2)
> do_task_delta_exec() require it.
>
> And then, 64bit can avoid holds rq lock when add_delta is false.
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> ---
> kernel/sched/core.c | 6 ++++++
> 1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index b817e6d..24ba1c6 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2657,6 +2657,12 @@ unsigned long long task_sched_runtime(struct task_struct *p, bool add_delta)
> struct rq *rq;
> u64 ns = 0;
>
> + /* Micro optimization. */

Instead of the above; how about something like:

/* 64-bit doesn't need locks to atomically read a 64bit value */

> +#ifdef CONFIG_64BIT
> + if (!add_delta)
> + return p->se.sum_exec_runtime;
> +#endif
> +
> rq = task_rq_lock(p, &flags);
> ns = p->se.sum_exec_runtime;
> if (add_delta)
> --
> 1.7.1
>


\
 
 \ /
  Last update: 2013-05-01 13:41    [W:0.309 / U:0.432 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site