[Intel-xe] [PATCH v4 02/10] drm/sched: Convert drm scheduler to use a work queue rather than kthread
Luben Tuikov
luben.tuikov at amd.com
Wed Oct 11 23:10:40 UTC 2023
On 2023-10-06 03:59, Tvrtko Ursulin wrote:
>
> On 05/10/2023 05:13, Luben Tuikov wrote:
>> On 2023-10-04 23:33, Matthew Brost wrote:
>>> On Tue, Sep 26, 2023 at 11:32:10PM -0400, Luben Tuikov wrote:
>>>> Hi,
>>>>
>>>> On 2023-09-19 01:01, Matthew Brost wrote:
>>>>> In XE, the new Intel GPU driver, a choice has made to have a 1 to 1
>>>>> mapping between a drm_gpu_scheduler and drm_sched_entity. At first this
>>>>> seems a bit odd but let us explain the reasoning below.
>>>>>
>>>>> 1. In XE the submission order from multiple drm_sched_entity is not
>>>>> guaranteed to be the same completion even if targeting the same hardware
>>>>> engine. This is because in XE we have a firmware scheduler, the GuC,
>>>>> which allowed to reorder, timeslice, and preempt submissions. If a using
>>>>> shared drm_gpu_scheduler across multiple drm_sched_entity, the TDR falls
>>>>> apart as the TDR expects submission order == completion order. Using a
>>>>> dedicated drm_gpu_scheduler per drm_sched_entity solve this problem.
>>>>>
>>>>> 2. In XE submissions are done via programming a ring buffer (circular
>>>>> buffer), a drm_gpu_scheduler provides a limit on number of jobs, if the
>>>>> limit of number jobs is set to RING_SIZE / MAX_SIZE_PER_JOB we get flow
>>>>> control on the ring for free.
>>>>>
>>>>> A problem with this design is currently a drm_gpu_scheduler uses a
>>>>> kthread for submission / job cleanup. This doesn't scale if a large
>>>>> number of drm_gpu_scheduler are used. To work around the scaling issue,
>>>>> use a worker rather than kthread for submission / job cleanup.
>>>>>
>>>>> v2:
>>>>> - (Rob Clark) Fix msm build
>>>>> - Pass in run work queue
>>>>> v3:
>>>>> - (Boris) don't have loop in worker
>>>>> v4:
>>>>> - (Tvrtko) break out submit ready, stop, start helpers into own patch
>>>>> v5:
>>>>> - (Boris) default to ordered work queue
>>>>>
>>>>> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
>>>>> ---
>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
>>>>> drivers/gpu/drm/etnaviv/etnaviv_sched.c | 2 +-
>>>>> drivers/gpu/drm/lima/lima_sched.c | 2 +-
>>>>> drivers/gpu/drm/msm/msm_ringbuffer.c | 2 +-
>>>>> drivers/gpu/drm/nouveau/nouveau_sched.c | 2 +-
>>>>> drivers/gpu/drm/panfrost/panfrost_job.c | 2 +-
>>>>> drivers/gpu/drm/scheduler/sched_main.c | 118 ++++++++++-----------
>>>>> drivers/gpu/drm/v3d/v3d_sched.c | 10 +-
>>>>> include/drm/gpu_scheduler.h | 14 ++-
>>>>> 9 files changed, 79 insertions(+), 75 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>> index e366f61c3aed..16f3cfe1574a 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>> @@ -2279,7 +2279,7 @@ static int amdgpu_device_init_schedulers(struct amdgpu_device *adev)
>>>>> break;
>>>>> }
>>>>>
>>>>> - r = drm_sched_init(&ring->sched, &amdgpu_sched_ops,
>>>>> + r = drm_sched_init(&ring->sched, &amdgpu_sched_ops, NULL,
>>>>> ring->num_hw_submission, 0,
>>>>> timeout, adev->reset_domain->wq,
>>>>> ring->sched_score, ring->name,
>>>>> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_sched.c b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
>>>>> index 345fec6cb1a4..618a804ddc34 100644
>>>>> --- a/drivers/gpu/drm/etnaviv/etnaviv_sched.c
>>>>> +++ b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
>>>>> @@ -134,7 +134,7 @@ int etnaviv_sched_init(struct etnaviv_gpu *gpu)
>>>>> {
>>>>> int ret;
>>>>>
>>>>> - ret = drm_sched_init(&gpu->sched, &etnaviv_sched_ops,
>>>>> + ret = drm_sched_init(&gpu->sched, &etnaviv_sched_ops, NULL,
>>>>> etnaviv_hw_jobs_limit, etnaviv_job_hang_limit,
>>>>> msecs_to_jiffies(500), NULL, NULL,
>>>>> dev_name(gpu->dev), gpu->dev);
>>>>> diff --git a/drivers/gpu/drm/lima/lima_sched.c b/drivers/gpu/drm/lima/lima_sched.c
>>>>> index ffd91a5ee299..8d858aed0e56 100644
>>>>> --- a/drivers/gpu/drm/lima/lima_sched.c
>>>>> +++ b/drivers/gpu/drm/lima/lima_sched.c
>>>>> @@ -488,7 +488,7 @@ int lima_sched_pipe_init(struct lima_sched_pipe *pipe, const char *name)
>>>>>
>>>>> INIT_WORK(&pipe->recover_work, lima_sched_recover_work);
>>>>>
>>>>> - return drm_sched_init(&pipe->base, &lima_sched_ops, 1,
>>>>> + return drm_sched_init(&pipe->base, &lima_sched_ops, NULL, 1,
>>>>> lima_job_hang_limit,
>>>>> msecs_to_jiffies(timeout), NULL,
>>>>> NULL, name, pipe->ldev->dev);
>>>>> diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.c b/drivers/gpu/drm/msm/msm_ringbuffer.c
>>>>> index 40c0bc35a44c..b8865e61b40f 100644
>>>>> --- a/drivers/gpu/drm/msm/msm_ringbuffer.c
>>>>> +++ b/drivers/gpu/drm/msm/msm_ringbuffer.c
>>>>> @@ -94,7 +94,7 @@ struct msm_ringbuffer *msm_ringbuffer_new(struct msm_gpu *gpu, int id,
>>>>> /* currently managing hangcheck ourselves: */
>>>>> sched_timeout = MAX_SCHEDULE_TIMEOUT;
>>>>>
>>>>> - ret = drm_sched_init(&ring->sched, &msm_sched_ops,
>>>>> + ret = drm_sched_init(&ring->sched, &msm_sched_ops, NULL,
>>>>> num_hw_submissions, 0, sched_timeout,
>>>>> NULL, NULL, to_msm_bo(ring->bo)->name, gpu->dev->dev);
>>>>
>>>> checkpatch.pl complains here about unmatched open parens.
>>>>
>>>
>>> Will fix and run checkpatch before posting next rev.
>>>
>>>>> if (ret) {
>>>>> diff --git a/drivers/gpu/drm/nouveau/nouveau_sched.c b/drivers/gpu/drm/nouveau/nouveau_sched.c
>>>>> index 88217185e0f3..d458c2227d4f 100644
>>>>> --- a/drivers/gpu/drm/nouveau/nouveau_sched.c
>>>>> +++ b/drivers/gpu/drm/nouveau/nouveau_sched.c
>>>>> @@ -429,7 +429,7 @@ int nouveau_sched_init(struct nouveau_drm *drm)
>>>>> if (!drm->sched_wq)
>>>>> return -ENOMEM;
>>>>>
>>>>> - return drm_sched_init(sched, &nouveau_sched_ops,
>>>>> + return drm_sched_init(sched, &nouveau_sched_ops, NULL,
>>>>> NOUVEAU_SCHED_HW_SUBMISSIONS, 0, job_hang_limit,
>>>>> NULL, NULL, "nouveau_sched", drm->dev->dev);
>>>>> }
>>>>> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
>>>>> index 033f5e684707..326ca1ddf1d7 100644
>>>>> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
>>>>> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
>>>>> @@ -831,7 +831,7 @@ int panfrost_job_init(struct panfrost_device *pfdev)
>>>>> js->queue[j].fence_context = dma_fence_context_alloc(1);
>>>>>
>>>>> ret = drm_sched_init(&js->queue[j].sched,
>>>>> - &panfrost_sched_ops,
>>>>> + &panfrost_sched_ops, NULL,
>>>>> nentries, 0,
>>>>> msecs_to_jiffies(JOB_TIMEOUT_MS),
>>>>> pfdev->reset.wq,
>>>>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
>>>>> index e4fa62abca41..ee6281942e36 100644
>>>>> --- a/drivers/gpu/drm/scheduler/sched_main.c
>>>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
>>>>> @@ -48,7 +48,6 @@
>>>>> * through the jobs entity pointer.
>>>>> */
>>>>>
>>>>> -#include <linux/kthread.h>
>>>>> #include <linux/wait.h>
>>>>> #include <linux/sched.h>
>>>>> #include <linux/completion.h>
>>>>> @@ -256,6 +255,16 @@ drm_sched_rq_select_entity_fifo(struct drm_sched_rq *rq)
>>>>> return rb ? rb_entry(rb, struct drm_sched_entity, rb_tree_node) : NULL;
>>>>> }
>>>>>
>>>>> +/**
>>>>> + * drm_sched_submit_queue - scheduler queue submission
>>>>
>>>> There is no verb in the description, and is not clear what
>>>> this function does unless one reads the code. Given that this
>>>> is DOC, this should be clearer here. Something like "queue
>>>> scheduler work to be executed" or something to that effect.
>>>>
>>>
>>> Will fix.
>>>
>>>> Coming back to this from reading the patch below, it was somewhat
>>>> unclear what "drm_sched_submit_queue()" does, since when reading
>>>> below, "submit" was being read by my mind as an adjective, as opposed
>>>> to a verb. Perhaps something like:
>>>>
>>>> drm_sched_queue_submit(), or
>>>> drm_sched_queue_exec(), or
>>>> drm_sched_queue_push(), or something to that effect. You pick. :-)
>>>>
>>>
>>> I prefer the name as is. In this patch we have:
>>>
>>> drm_sched_submit_queue()
>>> drm_sched_submit_start)
>>> drm_sched_submit_stop()
>>> drm_sched_submit_ready()
>>>
>>> I like all these functions start with 'drm_sched_submit' which allows
>>> for easy searching for the functions that touch the DRM scheduler
>>> submission state.
>>>
>>> With a little better doc are you fine with the names as is.
>>
>> Notice the following scheme in the naming,
>>
>> drm_sched_submit_queue()
>> drm_sched_submit_start)
>> drm_sched_submit_stop()
>> drm_sched_submit_ready()
>> \---+---/ \--+-/ \-+-/
>> | | +---> a verb
>> | +---------> should be a noun (something in the component)
>> +------------------> the kernel/software component
>>
>> And although "queue" can technically be used as a verb too, I'd rather it be "enqueue",
>> like this:
>>
>> drm_sched_submit_enqueue()
>>
>> And using "submit" as the noun of the component is a bit cringy,
>> since "submit" is really a verb, and it's cringy to make it a "state"
>> or an "object" we operate on in the DRM Scheduler. "Submission" is
>> a noun, but "submission enqueue/start/stop/ready" doesn't sound
>> very well thought out. "Submission" really is what the work-queue
>> does.
>>
>> I'd rather it be a real object, like for instance,
>>
>> drm_sched_wqueue_enqueue()
>> drm_sched_wqueue_start)
>> drm_sched_wqueue_stop()
>> drm_sched_wqueue_ready()
>>
>> Which tells me that the component is the DRM Scheduler, the object is a/the work-queue,
>> and the last word as the verb, is the action we're performing on the object, i.e. the work-queue.
>> Plus, all these functions actually do operate on work-queues, directly or indirectly,
>> are new, so it's a win-win naming scheme.
>>
>> I think that that would be most likeable.
>
> FWIW I was suggesting not to encode the fact submit queue is implemented
No. Overengineering.
> with a workqueue in the API name. IMO it would be nicer and less
> maintenance churn should something channge if the external components
> can be isolated from that detail.
>
> drm_sched_submit_queue_$verb? If not viewed as too verbose...
No.
That sounds like an unnecessary overengineering: "what if". No.
--
Regards,
Luben
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