Re: [PATCH 3/6] drm/scheduler: Job timeout handler returns status

[Christian König <christian.koenig@xxxxxxx>]

Am 25.11.20 um 12:04 schrieb Steven Price:
> On 25/11/2020 03:17, Luben Tuikov wrote:
> > The job timeout handler now returns status
> > indicating back to the DRM layer whether the job
> > was successfully cancelled or whether more time
> > should be given to the job to complete.
>
> I'm not sure I understand in what circumstances you would want to give 
> the job more time to complete. Could you expand on that?
>
> One thing we're missing at the moment in Panfrost is the ability to 
> suspend ("soft stop" is the Mali jargon) a job and pick something else 
> to run. The propitiatory driver stack uses this to avoid timing out 
> long running jobs while still allowing other processes to have time on 
> the GPU. But this interface as it stands doesn't seem to provide that.

On AMD hardware we call this IB preemption and it is indeed not handled 
very well by the scheduler at the moment.

See how the amdgpu code messes with the preempted IBs to restart them 
for example.

Christian.

> As the kernel test robot has already pointed out - you'll need to at 
> the very least update the other uses of this interface.
>
> Steve
>
> > Signed-off-by: Luben Tuikov <luben.tuikov@xxxxxxx>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_job.c |  6 ++++--
> >   include/drm/gpu_scheduler.h             | 13 ++++++++++---
> >   2 files changed, 14 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c 
> > b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> > index ff48101bab55..81b73790ecc6 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
> > @@ -28,7 +28,7 @@
> >   #include "amdgpu.h"
> >   #include "amdgpu_trace.h"
> >   -static void amdgpu_job_timedout(struct drm_sched_job *s_job)
> > +static int amdgpu_job_timedout(struct drm_sched_job *s_job)
> >   {
> >       struct amdgpu_ring *ring = to_amdgpu_ring(s_job->sched);
> >       struct amdgpu_job *job = to_amdgpu_job(s_job);
> > @@ -41,7 +41,7 @@ static void amdgpu_job_timedout(struct 
> > drm_sched_job *s_job)
> >           amdgpu_ring_soft_recovery(ring, job->vmid, 
> > s_job->s_fence->parent)) {
> >           DRM_ERROR("ring %s timeout, but soft recovered\n",
> >                 s_job->sched->name);
> > -        return;
> > +        return 0;
> >       }
> >         amdgpu_vm_get_task_info(ring->adev, job->pasid, &ti);
> > @@ -53,10 +53,12 @@ static void amdgpu_job_timedout(struct 
> > drm_sched_job *s_job)
> >         if (amdgpu_device_should_recover_gpu(ring->adev)) {
> >           amdgpu_device_gpu_recover(ring->adev, job);
> > +        return 0;
> >       } else {
> >           drm_sched_suspend_timeout(&ring->sched);
> >           if (amdgpu_sriov_vf(adev))
> >               adev->virt.tdr_debug = true;
> > +        return 1;
> >       }
> >   }
> >   diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> > index 2e0c368e19f6..61f7121e1c19 100644
> > --- a/include/drm/gpu_scheduler.h
> > +++ b/include/drm/gpu_scheduler.h
> > @@ -230,10 +230,17 @@ struct drm_sched_backend_ops {
> >       struct dma_fence *(*run_job)(struct drm_sched_job *sched_job);
> >         /**
> > -         * @timedout_job: Called when a job has taken too long to 
> > execute,
> > -         * to trigger GPU recovery.
> > +     * @timedout_job: Called when a job has taken too long to execute,
> > +     * to trigger GPU recovery.
> > +     *
> > +     * Return 0, if the job has been aborted successfully and will
> > +     * never be heard of from the device. Return non-zero if the
> > +     * job wasn't able to be aborted, i.e. if more time should be
> > +     * given to this job. The result is not "bool" as this
> > +     * function is not a predicate, although its result may seem
> > +     * as one.
> >        */
> > -    void (*timedout_job)(struct drm_sched_job *sched_job);
> > +    int (*timedout_job)(struct drm_sched_job *sched_job);
> >         /**
> >            * @free_job: Called once the job's finished fence has been 
> > signaled

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