On Tue, May 24, 2022 at 6:45 AM Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> wrote: > > > On 23/05/2022 23:53, Rob Clark wrote: > > On Mon, May 23, 2022 at 7:45 AM Tvrtko Ursulin > > <tvrtko.ursulin@xxxxxxxxxxxxxxx> wrote: > >> > >> > >> Hi Rob, > >> > >> On 28/07/2021 02:06, Rob Clark wrote: > >>> From: Rob Clark <robdclark@xxxxxxxxxxxx> > >>> > >>> The drm/scheduler provides additional prioritization on top of that > >>> provided by however many number of ringbuffers (each with their own > >>> priority level) is supported on a given generation. Expose the > >>> additional levels of priority to userspace and map the userspace > >>> priority back to ring (first level of priority) and schedular priority > >>> (additional priority levels within the ring). > >>> > >>> Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx> > >>> Acked-by: Christian König <christian.koenig@xxxxxxx> > >>> --- > >>> drivers/gpu/drm/msm/adreno/adreno_gpu.c | 4 +- > >>> drivers/gpu/drm/msm/msm_gem_submit.c | 4 +- > >>> drivers/gpu/drm/msm/msm_gpu.h | 58 ++++++++++++++++++++++++- > >>> drivers/gpu/drm/msm/msm_submitqueue.c | 35 +++++++-------- > >>> include/uapi/drm/msm_drm.h | 14 +++++- > >>> 5 files changed, 88 insertions(+), 27 deletions(-) > >>> > >>> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c > >>> index bad4809b68ef..748665232d29 100644 > >>> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c > >>> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c > >>> @@ -261,8 +261,8 @@ int adreno_get_param(struct msm_gpu *gpu, uint32_t param, uint64_t *value) > >>> return ret; > >>> } > >>> return -EINVAL; > >>> - case MSM_PARAM_NR_RINGS: > >>> - *value = gpu->nr_rings; > >>> + case MSM_PARAM_PRIORITIES: > >>> + *value = gpu->nr_rings * NR_SCHED_PRIORITIES; > >>> return 0; > >>> case MSM_PARAM_PP_PGTABLE: > >>> *value = 0; > >>> diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c > >>> index 450efe59abb5..c2ecec5b11c4 100644 > >>> --- a/drivers/gpu/drm/msm/msm_gem_submit.c > >>> +++ b/drivers/gpu/drm/msm/msm_gem_submit.c > >>> @@ -59,7 +59,7 @@ static struct msm_gem_submit *submit_create(struct drm_device *dev, > >>> submit->gpu = gpu; > >>> submit->cmd = (void *)&submit->bos[nr_bos]; > >>> submit->queue = queue; > >>> - submit->ring = gpu->rb[queue->prio]; > >>> + submit->ring = gpu->rb[queue->ring_nr]; > >>> submit->fault_dumped = false; > >>> > >>> INIT_LIST_HEAD(&submit->node); > >>> @@ -749,7 +749,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data, > >>> /* Get a unique identifier for the submission for logging purposes */ > >>> submitid = atomic_inc_return(&ident) - 1; > >>> > >>> - ring = gpu->rb[queue->prio]; > >>> + ring = gpu->rb[queue->ring_nr]; > >>> trace_msm_gpu_submit(pid_nr(pid), ring->id, submitid, > >>> args->nr_bos, args->nr_cmds); > >>> > >>> diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h > >>> index b912cacaecc0..0e4b45bff2e6 100644 > >>> --- a/drivers/gpu/drm/msm/msm_gpu.h > >>> +++ b/drivers/gpu/drm/msm/msm_gpu.h > >>> @@ -250,6 +250,59 @@ struct msm_gpu_perfcntr { > >>> const char *name; > >>> }; > >>> > >>> +/* > >>> + * The number of priority levels provided by drm gpu scheduler. The > >>> + * 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_MIN) > >>> + > >>> +/** > >>> + * msm_gpu_convert_priority - Map userspace priority to ring # and sched priority > >>> + * > >>> + * @gpu: the gpu instance > >>> + * @prio: the userspace priority level > >>> + * @ring_nr: [out] the ringbuffer the userspace priority maps to > >>> + * @sched_prio: [out] the gpu scheduler priority level which the userspace > >>> + * priority maps to > >>> + * > >>> + * With drm/scheduler providing it's own level of prioritization, our total > >>> + * number of available priority levels is (nr_rings * NR_SCHED_PRIORITIES). > >>> + * Each ring is associated with it's own scheduler instance. However, our > >>> + * UABI is that lower numerical values are higher priority. So mapping the > >>> + * single userspace priority level into ring_nr and sched_prio takes some > >>> + * care. The userspace provided priority (when a submitqueue is created) > >>> + * is mapped to ring nr and scheduler priority as such: > >>> + * > >>> + * ring_nr = userspace_prio / NR_SCHED_PRIORITIES > >>> + * sched_prio = NR_SCHED_PRIORITIES - > >>> + * (userspace_prio % NR_SCHED_PRIORITIES) - 1 > >>> + * > >>> + * This allows generations without preemption (nr_rings==1) to have some > >>> + * amount of prioritization, and provides more priority levels for gens > >>> + * that do have preemption. > >> > >> I am exploring how different drivers handle priority levels and this > >> caught my eye. > >> > >> Is the implication of the last paragraphs that on hw with nr_rings > 1, > >> ring + 1 preempts ring? > > > > Other way around, at least from the uabi standpoint. Ie. ring[0] > > preempts ring[1] > > Ah yes, I figure it out from the comments but then confused myself when > writing the email. > > >> If so I am wondering does the "spreading" of > >> user visible priorities by NR_SCHED_PRIORITIES creates a non-preemptable > >> levels within every "bucket" or how does that work? > > > > So, preemption is possible between any priority level before run_job() > > gets called, which writes the job into the ringbuffer. After that > > Hmm how? Before run_job() the jobs are not runnable, sitting in the > scheduler queues, right? I mean, if prio[0]+prio[1]+prio[2] map to a single ring, submit A on prio[1] could be executed after submit B on prio[2] provided that run_job(submitA) hasn't happened yet. So I guess it isn't "really" preemption because the submit hasn't started running on the GPU yet. But rather just scheduling according to priority. > > point, you only have "bucket" level preemption, because > > NR_SCHED_PRIORITIES levels of priority get mapped to a single FIFO > > ringbuffer. > > Right, and you have one GPU with four rings, which means you expose 12 > priority levels to userspace, did I get that right? Correct > If so how do you convey in the ABI that not all there priority levels > are equal? Like userspace can submit at prio 4 and expect prio 3 to > preempt, as would prio 2 preempt prio 3. While actual behaviour will not > match - 3 will not preempt 4. It isn't really exposed to userspace, but perhaps it should be.. Userspace just knows that, to the extent possible, the kernel will try to execute prio 3 before prio 4. > Also, does your userspace stack (EGL/Vulkan) use the priorities? I had a > quick peek in Mesa but did not spot it - although I am not really at > home there yet so maybe I missed it. Yes, there is an EGL extension: https://www.khronos.org/registry/EGL/extensions/IMG/EGL_IMG_context_priority.txt It is pretty limited, it only exposes three priority levels. BR, -R > > ----- > > > > btw, one fun (but unrelated) issue I'm hitting with scheduler... I'm > > trying to add an igt test to stress shrinker/eviction, similar to the > > existing tests/i915/gem_shrink.c. But we hit an unfortunate > > combination of circumstances: > > 1. Pinning memory happens in the synchronous part of the submit ioctl, > > before enqueuing the job for the kthread to handle. > > 2. The first run_job() callback incurs a slight delay (~1.5ms) while > > resuming the GPU > > 3. Because of that delay, userspace has a chance to queue up enough > > more jobs to require locking/pinning more than the available system > > RAM.. > > Is that one or multiple threads submitting jobs? > > > I'm not sure if we want a way to prevent userspace from getting *too* > > far ahead of the kthread. Or maybe at some point the shrinker should > > sleep on non-idle buffers? > > On the direct reclaim path when invoked from the submit ioctl? In i915 > we only shrink idle objects on direct reclaim and leave active ones for > the swapper. It depends on how your locking looks like whether you could > do them, whether there would be coupling of locks and fs-reclaim context. > > Regards, > > Tvrtko > > > BR, > > -R > > > >> > >> Regards, > >> > >> Tvrtko > >> > >>> + */ > >>> +static inline int msm_gpu_convert_priority(struct msm_gpu *gpu, int prio, > >>> + unsigned *ring_nr, enum drm_sched_priority *sched_prio) > >>> +{ > >>> + unsigned rn, sp; > >>> + > >>> + rn = div_u64_rem(prio, NR_SCHED_PRIORITIES, &sp); > >>> + > >>> + /* invert sched priority to map to higher-numeric-is-higher- > >>> + * priority convention > >>> + */ > >>> + sp = NR_SCHED_PRIORITIES - sp - 1; > >>> + > >>> + if (rn >= gpu->nr_rings) > >>> + return -EINVAL; > >>> + > >>> + *ring_nr = rn; > >>> + *sched_prio = sp; > >>> + > >>> + return 0; > >>> +} > >>> + > >>> /** > >>> * A submitqueue is associated with a gl context or vk queue (or equiv) > >>> * in userspace. > >>> @@ -257,7 +310,8 @@ struct msm_gpu_perfcntr { > >>> * @id: userspace id for the submitqueue, unique within the drm_file > >>> * @flags: userspace flags for the submitqueue, specified at creation > >>> * (currently unusued) > >>> - * @prio: the submitqueue priority > >>> + * @ring_nr: the ringbuffer used by this submitqueue, which is determined > >>> + * by the submitqueue's priority > >>> * @faults: the number of GPU hangs associated with this submitqueue > >>> * @ctx: the per-drm_file context associated with the submitqueue (ie. > >>> * which set of pgtables do submits jobs associated with the > >>> @@ -272,7 +326,7 @@ struct msm_gpu_perfcntr { > >>> struct msm_gpu_submitqueue { > >>> int id; > >>> u32 flags; > >>> - u32 prio; > >>> + u32 ring_nr; > >>> int faults; > >>> struct msm_file_private *ctx; > >>> struct list_head node; > >>> diff --git a/drivers/gpu/drm/msm/msm_submitqueue.c b/drivers/gpu/drm/msm/msm_submitqueue.c > >>> index 682ba2a7c0ec..32a55d81b58b 100644 > >>> --- a/drivers/gpu/drm/msm/msm_submitqueue.c > >>> +++ b/drivers/gpu/drm/msm/msm_submitqueue.c > >>> @@ -68,6 +68,8 @@ int msm_submitqueue_create(struct drm_device *drm, struct msm_file_private *ctx, > >>> struct msm_gpu_submitqueue *queue; > >>> struct msm_ringbuffer *ring; > >>> struct drm_gpu_scheduler *sched; > >>> + enum drm_sched_priority sched_prio; > >>> + unsigned ring_nr; > >>> int ret; > >>> > >>> if (!ctx) > >>> @@ -76,8 +78,9 @@ int msm_submitqueue_create(struct drm_device *drm, struct msm_file_private *ctx, > >>> if (!priv->gpu) > >>> return -ENODEV; > >>> > >>> - if (prio >= priv->gpu->nr_rings) > >>> - return -EINVAL; > >>> + ret = msm_gpu_convert_priority(priv->gpu, prio, &ring_nr, &sched_prio); > >>> + if (ret) > >>> + return ret; > >>> > >>> queue = kzalloc(sizeof(*queue), GFP_KERNEL); > >>> > >>> @@ -86,24 +89,13 @@ int msm_submitqueue_create(struct drm_device *drm, struct msm_file_private *ctx, > >>> > >>> kref_init(&queue->ref); > >>> queue->flags = flags; > >>> - queue->prio = prio; > >>> + queue->ring_nr = ring_nr; > >>> > >>> - ring = priv->gpu->rb[prio]; > >>> + ring = priv->gpu->rb[ring_nr]; > >>> sched = &ring->sched; > >>> > >>> - /* > >>> - * TODO we can allow more priorities than we have ringbuffers by > >>> - * mapping: > >>> - * > >>> - * ring = prio / 3; > >>> - * ent_prio = DRM_SCHED_PRIORITY_MIN + (prio % 3); > >>> - * > >>> - * Probably avoid using DRM_SCHED_PRIORITY_KERNEL as that is > >>> - * treated specially in places. > >>> - */ > >>> ret = drm_sched_entity_init(&queue->entity, > >>> - DRM_SCHED_PRIORITY_NORMAL, > >>> - &sched, 1, NULL); > >>> + sched_prio, &sched, 1, NULL); > >>> if (ret) { > >>> kfree(queue); > >>> return ret; > >>> @@ -134,16 +126,19 @@ int msm_submitqueue_create(struct drm_device *drm, struct msm_file_private *ctx, > >>> int msm_submitqueue_init(struct drm_device *drm, struct msm_file_private *ctx) > >>> { > >>> struct msm_drm_private *priv = drm->dev_private; > >>> - int default_prio; > >>> + int default_prio, max_priority; > >>> > >>> if (!priv->gpu) > >>> return -ENODEV; > >>> > >>> + max_priority = (priv->gpu->nr_rings * NR_SCHED_PRIORITIES) - 1; > >>> + > >>> /* > >>> - * Select priority 2 as the "default priority" unless nr_rings is less > >>> - * than 2 and then pick the lowest priority > >>> + * Pick a medium priority level as default. Lower numeric value is > >>> + * higher priority, so round-up to pick a priority that is not higher > >>> + * than the middle priority level. > >>> */ > >>> - default_prio = clamp_t(uint32_t, 2, 0, priv->gpu->nr_rings - 1); > >>> + default_prio = DIV_ROUND_UP(max_priority, 2); > >>> > >>> INIT_LIST_HEAD(&ctx->submitqueues); > >>> > >>> diff --git a/include/uapi/drm/msm_drm.h b/include/uapi/drm/msm_drm.h > >>> index f075851021c3..6b8fffc28a50 100644 > >>> --- a/include/uapi/drm/msm_drm.h > >>> +++ b/include/uapi/drm/msm_drm.h > >>> @@ -73,11 +73,19 @@ struct drm_msm_timespec { > >>> #define MSM_PARAM_MAX_FREQ 0x04 > >>> #define MSM_PARAM_TIMESTAMP 0x05 > >>> #define MSM_PARAM_GMEM_BASE 0x06 > >>> -#define MSM_PARAM_NR_RINGS 0x07 > >>> +#define MSM_PARAM_PRIORITIES 0x07 /* The # of priority levels */ > >>> #define MSM_PARAM_PP_PGTABLE 0x08 /* => 1 for per-process pagetables, else 0 */ > >>> #define MSM_PARAM_FAULTS 0x09 > >>> #define MSM_PARAM_SUSPENDS 0x0a > >>> > >>> +/* For backwards compat. The original support for preemption was based on > >>> + * a single ring per priority level so # of priority levels equals the # > >>> + * of rings. With drm/scheduler providing additional levels of priority, > >>> + * the number of priorities is greater than the # of rings. The param is > >>> + * renamed to better reflect this. > >>> + */ > >>> +#define MSM_PARAM_NR_RINGS MSM_PARAM_PRIORITIES > >>> + > >>> struct drm_msm_param { > >>> __u32 pipe; /* in, MSM_PIPE_x */ > >>> __u32 param; /* in, MSM_PARAM_x */ > >>> @@ -304,6 +312,10 @@ struct drm_msm_gem_madvise { > >>> > >>> #define MSM_SUBMITQUEUE_FLAGS (0) > >>> > >>> +/* > >>> + * The submitqueue priority should be between 0 and MSM_PARAM_PRIORITIES-1, > >>> + * a lower numeric value is higher priority. > >>> + */ > >>> struct drm_msm_submitqueue { > >>> __u32 flags; /* in, MSM_SUBMITQUEUE_x */ > >>> __u32 prio; /* in, Priority level */