linux-kernel - Re: [PATCH v1 4/6] drm/lima: handle spurious timeouts due to high irq latency

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Message-ID: <CAKGbVbtww65w+sr7OiccawRkGt-p3MRWaWNU=nkQTaqdyMxqVA@mail.gmail.com>
Date: Sun, 21 Jan 2024 19:20:14 +0800
From: Qiang Yu <yuq825@...il.com>
To: Hillf Danton <hdanton@...a.com>
Cc: Erico Nunes <nunes.erico@...il.com>, dri-devel@...ts.freedesktop.org, 
	lima@...ts.freedesktop.org, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 4/6] drm/lima: handle spurious timeouts due to high irq latency

On Sun, Jan 21, 2024 at 5:56 PM Hillf Danton <hdanton@...a.com> wrote:
>
> On Wed, 17 Jan 2024 04:12:10 +0100 Erico Nunes <nunes.erico@...il.com>
> >
> > @@ -401,9 +399,33 @@ static enum drm_gpu_sched_stat lima_sched_timedout_job(struct drm_sched_job *job
> >       struct lima_sched_pipe *pipe = to_lima_pipe(job->sched);
> >       struct lima_sched_task *task = to_lima_task(job);
> >       struct lima_device *ldev = pipe->ldev;
> > +     struct lima_ip *ip = pipe->processor[0];
> > +
> > +     /*
> > +      * If the GPU managed to complete this jobs fence, the timeout is
> > +      * spurious. Bail out.
> > +      */
> > +     if (dma_fence_is_signaled(task->done_fence)) {
> > +             DRM_WARN("%s spurious timeout\n", lima_ip_name(ip));
> > +             return DRM_GPU_SCHED_STAT_NOMINAL;
> > +     }
>
> Given 500ms in lima_sched_pipe_init(), no timeout is spurious by define,
> and stop selling bandaid like this because you have options like locating
> the reasons behind timeout.

This chang do look like to aim for 2FPS apps. Maybe 500ms is too short
for week mali4x0 gpus (2FPS apps appear more likely). AMD/NV GPU uses
10s timeout. So increasing the timeout seems to be an equivalent and better
way?

> > +
> > +     /*
> > +      * Lima IRQ handler may take a long time to process an interrupt
> > +      * if there is another IRQ handler hogging the processing.
> > +      * In order to catch such cases and not report spurious Lima job
> > +      * timeouts, synchronize the IRQ handler and re-check the fence
> > +      * status.
> > +      */
> > +     synchronize_irq(ip->irq);
> > +
> > +     if (dma_fence_is_signaled(task->done_fence)) {
> > +             DRM_WARN("%s unexpectedly high interrupt latency\n", lima_ip_name(ip));
> > +             return DRM_GPU_SCHED_STAT_NOMINAL;
> > +     }
> >
> >       if (!pipe->error)
> > -             DRM_ERROR("lima job timeout\n");
> > +             DRM_ERROR("%s lima job timeout\n", lima_ip_name(ip));
> >
> >       drm_sched_stop(&pipe->base, &task->base);
> >