linux-kernel - Re: [PATCHSET v2 sched_ext/for-6.11] sched_ext: Allow SCX_DSQ_LOCAL

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Message-ID: <ZpF0VrEKRRjyc_Tr@slm.duckdns.org>
Date: Fri, 12 Jul 2024 08:22:14 -1000
From: Tejun Heo <tj@...nel.org>
To: void@...ifault.com
Cc: linux-kernel@...r.kernel.org, kernel-team@...a.com,
	schatzberg.dan@...il.com, mingo@...hat.com, peterz@...radead.org,
	changwoo@...lia.com, righi.andrea@...il.com
Subject: Re: [PATCHSET v2 sched_ext/for-6.11] sched_ext: Allow
 SCX_DSQ_LOCAL_ON for direct dispatches

On Wed, Jul 10, 2024 at 03:13:57PM -1000, Tejun Heo wrote:
> This is v2. Changes from v1:
> (http://lkml.kernel.org/r/20240709212137.1199269-1-tj@kernel.org)
> 
> - 0003-sched_ext-Make-rf-optional-for-dispatch_to_local_dsq.patch is
>   replaced with
>   0003-sched_ext-Unpin-and-repin-rq-lock-from-balance_scx.patch.
>   balance_scx() now unpins the rq lock and the inner functions don't handle
>   rq pinning. This simplifies code quite a bit.
> 
> - schedule_deferred() was missing a return after balance_work scheduling.
>   Fixed.
> 
> - Other misc changes including UP build warning fix.
> 
> In ops.dispatch(), SCX_DSQ_LOCAL_ON can be used to dispatch the task to the
> local DSQ of any CPU. However, during direct dispatch from ops.select_cpu()
> and ops.enqueue(), this isn't allowed. This is because dispatching to the
> local DSQ of a remote CPU requires locking both the task's current and new
> rq's and such double locking can't be done directly from ops.enqueue(). This
> gap in API forces schedulers into work-arounds which are not straightforward
> or optimal such as skipping direct dispatches in such cases.
> 
> This patchset implements SCX_DSQ_LOCAL_ON support for direct dispatches.
> 
> This patchset contains the following patches:
> 
>  0001-sched-Move-struct-balance_callback-definition-upward.patch
>  0002-sched_ext-Open-code-task_linked_on_dsq.patch
>  0003-sched_ext-Unpin-and-repin-rq-lock-from-balance_scx.patch
>  0004-sched_ext-s-SCX_RQ_BALANCING-SCX_RQ_IN_BALANCE-and-a.patch
>  0005-sched_ext-Allow-SCX_DSQ_LOCAL_ON-for-direct-dispatch.patch
>  0006-sched_ext-scx_qmap-Pick-idle-CPU-for-direct-dispatch.patch

Applied to sched_ext/for-6.11.

Thanks.

-- 
tejun