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

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Message-ID: <Z_bFTQBweZf59CzC@slm.duckdns.org>
Date: Wed, 9 Apr 2025 09:06:53 -1000
From: Tejun Heo <tj@...nel.org>
To: void@...ifault.com, arighi@...dia.com, multics69@...il.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

On Tue, Apr 08, 2025 at 01:06:00PM -1000, 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

Applied to sched_ext/for-6.16.

Thanks.

-- 
tejun