From: Daniel Vetter <daniel@ffwll.ch>
To: Qais Yousef <qais.yousef@arm.com>
Cc: Rob Clark <robdclark@gmail.com>,
dri-devel <dri-devel@lists.freedesktop.org>,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
Tejun Heo <tj@kernel.org>, Tim Murray <timmurray@google.com>,
Daniel Vetter <daniel@ffwll.ch>,
Rob Clark <robdclark@chromium.org>,
open list <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>
Subject: Re: [PATCH v2 0/3] drm: commit_work scheduling
Date: Thu, 8 Oct 2020 11:10:17 +0200 [thread overview]
Message-ID: <20201008091017.GD438822@phenom.ffwll.local> (raw)
In-Reply-To: <20201007163010.bfgst6xfvkn2lzrk@e107158-lin.cambridge.arm.com>
On Wed, Oct 07, 2020 at 05:30:10PM +0100, Qais Yousef wrote:
> On 10/07/20 08:57, Rob Clark wrote:
> > Yeah, I think we will end up making some use of uclamp.. there is
> > someone else working on that angle
> >
> > But without it, this is a case that exposes legit prioritization
> > problems with commit_work which we should fix ;-)
>
> I wasn't suggesting this as an alternative to fixing the other problem. But it
> seemed you had a different problem here that I thought I could help with :-)
>
> I did give my opinion about how to handle that priority issue. If the 2 threads
> are kernel threads and by design they need relative priorities IMO the kernel
> need to be taught to set this relative priority. It seemed the vblank worker
> could run as SCHED_DEADLINE. If this works, then the priority problem for
> commit_work disappears as SCHED_DEADLINE will preempt RT. If commit_work uses
> sched_set_fifo(), its priority will be 50, hence your SF threads can no longer
> preempt it. And you can manage the SF threads to be any value you want relative
> to 50 anyway without having to manage commit_work itself.
>
> I'm not sure if you have problems with RT tasks preempting important CFS
> tasks. My brain registered two conflicting statements.
I think the problem is there's two modes cros runs in: Normal cros mode,
which mostly works like a linux desktop. CFS commit work seems fine.
Other mode is android emulation, where we have the surface flinger thread
running at SCHED_FIFO. I think Rob's plan is to runtime switch priorities
to match each use case.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
prev parent reply other threads:[~2020-10-08 9:10 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-30 21:17 [PATCH v2 0/3] drm: commit_work scheduling Rob Clark
2020-09-30 21:17 ` [PATCH v2 1/3] drm/crtc: Introduce per-crtc kworker Rob Clark
2020-09-30 21:17 ` [PATCH v2 2/3] drm/atomic: Use kthread worker for nonblocking commits Rob Clark
2020-09-30 21:17 ` [PATCH v2 3/3] drm: Expose CRTC's kworker task id Rob Clark
2020-10-01 7:25 ` [PATCH v2 0/3] drm: commit_work scheduling Daniel Vetter
2020-10-01 15:15 ` Rob Clark
2020-10-01 15:25 ` Daniel Vetter
2020-10-02 10:52 ` Ville Syrjälä
2020-10-02 11:05 ` Ville Syrjälä
2020-10-02 17:55 ` Rob Clark
2020-10-05 12:15 ` Ville Syrjälä
2020-10-05 14:15 ` Daniel Vetter
2020-10-05 22:58 ` Rob Clark
2020-10-07 16:44 ` Rob Clark
2020-10-08 8:24 ` Ville Syrjälä
2020-10-16 16:27 ` Rob Clark
2020-10-02 11:01 ` Qais Yousef
2020-10-02 18:07 ` Rob Clark
2020-10-05 15:00 ` Qais Yousef
2020-10-05 23:24 ` Rob Clark
2020-10-06 9:08 ` Daniel Vetter
2020-10-06 10:01 ` Peter Zijlstra
2020-10-06 10:59 ` Qais Yousef
2020-10-06 20:04 ` Rob Clark
2020-10-07 10:36 ` Qais Yousef
2020-10-07 15:57 ` Rob Clark
2020-10-07 16:30 ` Qais Yousef
2020-10-08 9:10 ` Daniel Vetter [this message]
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