Re: [PATCH 2/2] drm/sched: Reverse run-queue priority enumeration

["Christian König" <christian.koenig@amd.com>]

Am 24.11.23 um 09:22 schrieb Luben Tuikov:
> On 2023-11-24 03:04, Christian König wrote:
>> Am 24.11.23 um 06:27 schrieb Luben Tuikov:
>>> Reverse run-queue priority enumeration such that the higest priority is now 0,
>>> and for each consecutive integer the prioirty diminishes.
>>>
>>> Run-queues correspond to priorities. To an external observer a scheduler
>>> created with a single run-queue, and another created with
>>> DRM_SCHED_PRIORITY_COUNT number of run-queues, should always schedule
>>> sched->sched_rq[0] with the same "priority", as that index run-queue exists in
>>> both schedulers, i.e. a scheduler with one run-queue or many. This patch makes
>>> it so.
>>>
>>> In other words, the "priority" of sched->sched_rq[n], n >= 0, is the same for
>>> any scheduler created with any allowable number of run-queues (priorities), 0
>>> to DRM_SCHED_PRIORITY_COUNT.
>>>
>>> Cc: Rob Clark <robdclark@gmail.com>
>>> Cc: Abhinav Kumar <quic_abhinavk@quicinc.com>
>>> Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
>>> Cc: Danilo Krummrich <dakr@redhat.com>
>>> Cc: Alex Deucher <alexander.deucher@amd.com>
>>> Cc: Christian König <christian.koenig@amd.com>
>>> Cc: linux-arm-msm@vger.kernel.org
>>> Cc: freedreno@lists.freedesktop.org
>>> Cc: dri-devel@lists.freedesktop.org
>>> Signed-off-by: Luben Tuikov <ltuikov89@gmail.com>
>>> ---
>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_job.c  |  2 +-
>>>    drivers/gpu/drm/msm/msm_gpu.h            |  2 +-
>>>    drivers/gpu/drm/scheduler/sched_entity.c |  7 ++++---
>>>    drivers/gpu/drm/scheduler/sched_main.c   | 15 +++++++--------
>>>    include/drm/gpu_scheduler.h              |  6 +++---
>>>    5 files changed, 16 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
>>> index 1a25931607c514..71a5cf37b472d4 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_job.c
>>> @@ -325,7 +325,7 @@ void amdgpu_job_stop_all_jobs_on_sched(struct drm_gpu_scheduler *sched)
>>>    	int i;
>>>    
>>>    	/* Signal all jobs not yet scheduled */
>>> -	for (i = sched->num_rqs - 1; i >= DRM_SCHED_PRIORITY_LOW; i--) {
>>> +	for (i = DRM_SCHED_PRIORITY_KERNEL; i < sched->num_rqs; i++) {
>>>    		struct drm_sched_rq *rq = sched->sched_rq[i];
>>>    		spin_lock(&rq->lock);
>>>    		list_for_each_entry(s_entity, &rq->entities, list) {
>>> diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
>>> index eb0c97433e5f8a..2bfcb222e35338 100644
>>> --- a/drivers/gpu/drm/msm/msm_gpu.h
>>> +++ b/drivers/gpu/drm/msm/msm_gpu.h
>>> @@ -347,7 +347,7 @@ struct msm_gpu_perfcntr {
>>>     * DRM_SCHED_PRIORITY_KERNEL priority level is treated specially in some
>>>     * cases, so we don't use it (no need for kernel generated jobs).
>>>     */
>>> -#define NR_SCHED_PRIORITIES (1 + DRM_SCHED_PRIORITY_HIGH - DRM_SCHED_PRIORITY_LOW)
>>> +#define NR_SCHED_PRIORITIES (1 + DRM_SCHED_PRIORITY_LOW - DRM_SCHED_PRIORITY_HIGH)
>>>    
>>>    /**
>>>     * struct msm_file_private - per-drm_file context
>>> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
>>> index cb7445be3cbb4e..6e2b02e45e3a32 100644
>>> --- a/drivers/gpu/drm/scheduler/sched_entity.c
>>> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
>>> @@ -81,14 +81,15 @@ int drm_sched_entity_init(struct drm_sched_entity *entity,
>>>    		 */
>>>    		pr_warn("%s: called with uninitialized scheduler\n", __func__);
>>>    	} else if (num_sched_list) {
>>> -		/* The "priority" of an entity cannot exceed the number
>>> -		 * of run-queues of a scheduler.
>>> +		/* The "priority" of an entity cannot exceed the number of
>>> +		 * run-queues of a scheduler. Choose the lowest priority
>>> +		 * available.
>>>    		 */
>>>    		if (entity->priority >= sched_list[0]->num_rqs) {
>>>    			drm_err(sched_list[0], "entity with out-of-bounds priority:%u num_rqs:%u\n",
>>>    				entity->priority, sched_list[0]->num_rqs);
>>>    			entity->priority = max_t(s32, (s32) sched_list[0]->num_rqs - 1,
>>> -						 (s32) DRM_SCHED_PRIORITY_LOW);
>>> +						 (s32) DRM_SCHED_PRIORITY_KERNEL);
>> That seems to be a no-op. You basically say max_T(.., num_rqs - 1, 0),
>> this will always be num_rqs - 1
> This protects against num_rqs being equal to 0, in which case we select KERNEL (0).

Ah! That's also why convert it to signed! I was already wondering why 
you do this.

>
> This comes from "[PATCH] drm/sched: Fix bounds limiting when given a malformed entity"
> which I sent yesterday (Message-ID: <20231123122422.167832-2-ltuikov89@gmail.com>).

I can't find that one in my inbox anywhere, but was able to find it in 
patchwork.

> Could you R-B that patch too?

I would add a comment cause the intention of max_t(s32 is really not 
obvious here.

With that done feel free to add my rb to both patches.

Regards,
Christian.


>
>> Apart from that looks good to me.
> Okay, could you R-B this patch then.