[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 23:11:18 UTC 2023
On 2023-10-06 11:14, Matthew Brost wrote:
> On Fri, Oct 06, 2023 at 08:59:15AM +0100, 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()
>>>
>
> How about:
>
> drm_sched_submission_enqueue()
> drm_sched_submission_start)
> drm_sched_submission_stop()
> drm_sched_submission_ready()
No.
--
Regards,
Luben
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