* [PATCH 1/1] sched/fair:Avoid unnecessary assignment to cfs_rq->on_list
@ 2021-01-07 1:57 qianjun.kernel
2021-01-07 8:27 ` Vincent Guittot
0 siblings, 1 reply; 2+ messages in thread
From: qianjun.kernel @ 2021-01-07 1:57 UTC (permalink / raw)
To: mingo, peterz, juri.lelli, vincent.guittot, linux-kernel; +Cc: jun qian
From: jun qian <qianjun.kernel@gmail.com>
Obviously, cfs_rq->on_list is already equal to 1 when cfs_rq->on_list
is assigned a value of 1, so an else branch is needed to avoid unnecessary
assignment operations.
Signed-off-by: jun qian <qianjun.kernel@gmail.com>
---
kernel/sched/fair.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 04a3ce20da67..ef6ebd95443d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -305,8 +305,8 @@ static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
if (cfs_rq->on_list)
return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list;
-
- cfs_rq->on_list = 1;
+ else
+ cfs_rq->on_list = 1;
/*
* Ensure we either appear before our parent (if already
--
2.18.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH 1/1] sched/fair:Avoid unnecessary assignment to cfs_rq->on_list
2021-01-07 1:57 [PATCH 1/1] sched/fair:Avoid unnecessary assignment to cfs_rq->on_list qianjun.kernel
@ 2021-01-07 8:27 ` Vincent Guittot
0 siblings, 0 replies; 2+ messages in thread
From: Vincent Guittot @ 2021-01-07 8:27 UTC (permalink / raw)
To: qianjun.kernel; +Cc: Ingo Molnar, Peter Zijlstra, Juri Lelli, linux-kernel
On Thu, 7 Jan 2021 at 02:57, <qianjun.kernel@gmail.com> wrote:
>
> From: jun qian <qianjun.kernel@gmail.com>
>
> Obviously, cfs_rq->on_list is already equal to 1 when cfs_rq->on_list
> is assigned a value of 1, so an else branch is needed to avoid unnecessary
> assignment operations.
>
> Signed-off-by: jun qian <qianjun.kernel@gmail.com>
> ---
> kernel/sched/fair.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 04a3ce20da67..ef6ebd95443d 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -305,8 +305,8 @@ static inline bool list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
>
> if (cfs_rq->on_list)
> return rq->tmp_alone_branch == &rq->leaf_cfs_rq_list;
if cfs_rq->on_list == 1, list_add_leaf_cfs_rq() returns and will not
unnecessary set cfs_rq->on_list
so your change is useless but makes the code less readable
> -
> - cfs_rq->on_list = 1;
> + else
> + cfs_rq->on_list = 1;
>
> /*
> * Ensure we either appear before our parent (if already
> --
> 2.18.2
>
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2021-01-07 1:57 [PATCH 1/1] sched/fair:Avoid unnecessary assignment to cfs_rq->on_list qianjun.kernel
2021-01-07 8:27 ` Vincent Guittot
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