linux-kernel - Re: [PATCHSET sched_ext/for-6.16] sched_ext: Reduce usage of static

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Message-ID: <a536eeca-8e35-4986-9071-789260d0db49@gmail.com>
Date: Wed, 9 Apr 2025 10:37:15 +0900
From: Changwoo Min <multics69@...il.com>
To: Tejun Heo <tj@...nel.org>, void@...ifault.com, arighi@...dia.com,
 Changwoo Min <changwoo@...lia.com>
Cc: linux-kernel@...r.kernel.org, sched-ext@...a.com
Subject: Re: [PATCHSET sched_ext/for-6.16] sched_ext: Reduce usage of
 static_keys

Hi Tejun,

Thank you for the cleanup. Looks good to me.

Acked-by: Changwoo Min <changwoo@...lia.com>

Regards,
Changwoo Min

On 4/9/25 08:06, Tejun Heo wrote:
> sched_ext uses static_keys to optimize branches on ops flags and which ops
> are implemented. Some of those branches aren't that hot and while others are
> hotter, they are unlikely to cause meaningful overhead difference given
> everything else that's going on. static_keys were used more because there
> was no reason not to use static_keys. However, the planned multiple
> hierarchical scheduler support won't work with global static_keys as these
> branches would have to be based on the specific ops instance.
> 
> This patchset replaces static_key usages with tests on ops.flags and a
> bitmap tracking which operation is implemented. I couldn't see performance
> difference in numerous hackbench runs on a Ryzen 3990x machine before and
> after the patchset.
> 
> This patchset contains the following five patches:
> 
>   0001-sched_ext-Indentation-updates.patch
>   0002-sched_ext-Remove-scx_ops_enq_-static_keys.patch
>   0003-sched_ext-Remove-scx_ops_cpu_preempt-static_key.patch
>   0004-sched_ext-Remove-scx_ops_allow_queued_wakeup-static_.patch
>   0005-sched_ext-Make-scx_has_op-a-bitmap.patch
> 
> and is also available in the following git branch:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git scx-remove-static_keys
> 
> diffstat follows. Thanks.
> 
>   kernel/sched/ext.c |   91 +++++++++++++++++++++++------------------------------
>   kernel/sched/ext.h |    8 ----
>   2 files changed, 42 insertions(+), 57 deletions(-)
> 
> --
> tejun
>