linux-kernel - Re: [PATCH 2/4] drm/amdgpu: replace use of system_wq with system_percpu

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Message-ID: <0ea75705-2824-44ab-8583-4a06fbf61b10@amd.com>
Date: Mon, 3 Nov 2025 16:07:20 +0100
From: Christian König <christian.koenig@....com>
To: Marco Crivellari <marco.crivellari@...e.com>
Cc: linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org, Tejun Heo <tj@...nel.org>,
 Lai Jiangshan <jiangshanlai@...il.com>,
 Frederic Weisbecker <frederic@...nel.org>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Michal Hocko <mhocko@...e.com>, Alex Deucher <alexander.deucher@....com>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Subject: Re: [PATCH 2/4] drm/amdgpu: replace use of system_wq with
 system_percpu_wq



On 10/31/25 10:01, Marco Crivellari wrote:
> On Thu, Oct 30, 2025 at 6:10 PM Christian König
> <christian.koenig@....com> wrote:
>> [...]
>> In this particular use case we actually don't want the percpu wq.
>>
>> This can execute on any CPU except for the current one.
>>
>> Regards,
>> Christian.
>>
>>>  exit:
>>>       if (amdgpu_sriov_vf(adev)) {
>>
> 
> Hi Christian,
> 
> like for the unbound workqueue also the system_percpu_wq is just a
> rename for system_wq.
> Technically I changed the workqueue because we added in the code two wq:
> - system_percpu_wq
> - system_dfl_wq
> 
> You can see the commits mentioned in the cover letter, shared also below:
> 
> - commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq")
> - commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag")
> 
> So basically the behavior is the same.
> 
> But if it would be beneficial to have an unbound wq, I can send the v2
> with the change!

Please do so. The purpose of offloading that into a work item is to execute it on a different CPU.

I wasn't aware that the system_wq was CPU bound at all.

Thanks to taking care of that,
Christian.

> We did so also for other subsystems.
> 
> Thanks!
> 
> 
> 
> --
> 
> Marco Crivellari
> 
> L3 Support Engineer, Technology & Product