Re: [PATCH v4 1/4] drm/panthor: introduce job cycle and timestamp accounting

[Adrián Larumbe]

Hi Steven, thanks for the remarks.

On 19.07.2024 15:14, Steven Price wrote:
> On 16/07/2024 21:11, Adrián Larumbe wrote:
> > Enable calculations of job submission times in clock cycles and wall
> > time. This is done by expanding the boilerplate command stream when running
> > a job to include instructions that compute said times right before an after
> > a user CS.
> > 
> > Those numbers are stored in the queue's group's sync objects BO, right
> > after them. Because the queues in a group might have a different number of
> > slots, one must keep track of the overall slot tally when reckoning the
> > offset of a queue's time sample structs, one for each slot.
> > 
> > This commit is done in preparation for enabling DRM fdinfo support in the
> > Panthor driver, which depends on the numbers calculated herein.
> > 
> > A profile mode device flag has been added that will in a future commit
> > allow UM to toggle time sampling behaviour, which is disabled by default to
> > save power. It also enables marking jobs as being profiled and picks one of
> > two call instruction arrays to insert into the ring buffer. One of them
> > includes FW logic to sample the timestamp and cycle counter registers and
> > write them into the job's syncobj, and the other does not.
> > 
> > A profiled job's call sequence takes up two ring buffer slots, and this is
> > reflected when initialising the DRM scheduler for each queue, with a
> > profiled job contributing twice as many credits.
> > 
> > Signed-off-by: Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx>
> 
> Thanks for the updates, this looks better. A few minor comments below.
> 
> > ---
> >  drivers/gpu/drm/panthor/panthor_device.h |   2 +
> >  drivers/gpu/drm/panthor/panthor_sched.c  | 244 ++++++++++++++++++++---
> >  2 files changed, 216 insertions(+), 30 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
> > index e388c0472ba7..3ede2f80df73 100644
> > --- a/drivers/gpu/drm/panthor/panthor_device.h
> > +++ b/drivers/gpu/drm/panthor/panthor_device.h
> > @@ -162,6 +162,8 @@ struct panthor_device {
> >  		 */
> >  		struct page *dummy_latest_flush;
> >  	} pm;
> > +
> > +	bool profile_mode;
> >  };
> >  
> >  /**
> > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> > index 79ffcbc41d78..6438e5ea1f2b 100644
> > --- a/drivers/gpu/drm/panthor/panthor_sched.c
> > +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> > @@ -93,6 +93,9 @@
> >  #define MIN_CSGS				3
> >  #define MAX_CSG_PRIO				0xf
> >  
> > +#define NUM_INSTRS_PER_SLOT			16
> > +#define SLOTSIZE				(NUM_INSTRS_PER_SLOT * sizeof(u64))
> > +
> >  struct panthor_group;
> >  
> >  /**
> > @@ -466,6 +469,9 @@ struct panthor_queue {
> >  		 */
> >  		struct list_head in_flight_jobs;
> >  	} fence_ctx;
> > +
> > +	/** @time_offset: Offset of panthor_job_times structs in group's syncobj bo. */
> > +	unsigned long time_offset;
> 
> AFAICT this doesn't need to be stored. We could just pass this value
> into group_create_queue() as an extra parameter where it's used.

I think we need to keep this offset value around, because queues within the same group
could have a variable number of slots, so when fetching the sampled values from the
syncobjs BO in update_fdinfo_stats, it would have to traverse the entire array of
preceding queues and figure out their size in slots so as to jump over as many
struct panthor_job_times after the preceding syncobj array.

> >  };
> >  
> >  /**
> > @@ -592,7 +598,17 @@ struct panthor_group {
> >  	 * One sync object per queue. The position of the sync object is
> >  	 * determined by the queue index.
> >  	 */
> > -	struct panthor_kernel_bo *syncobjs;
> > +
> > +	struct {
> > +		/** @bo: Kernel BO holding the sync objects. */
> > +		struct panthor_kernel_bo *bo;
> > +
> > +		/**
> > +		 * @job_times_offset: Beginning of panthor_job_times struct samples after
> > +		 * the group's array of sync objects.
> > +		 */
> > +		size_t job_times_offset;
> > +	} syncobjs;
> >  
> >  	/** @state: Group state. */
> >  	enum panthor_group_state state;
> > @@ -651,6 +667,18 @@ struct panthor_group {
> >  	struct list_head wait_node;
> >  };
> >  
> > +struct panthor_job_times {
> > +	struct {
> > +		u64 before;
> > +		u64 after;
> > +	} cycles;
> > +
> > +	struct {
> > +		u64 before;
> > +		u64 after;
> > +	} time;
> > +};
> > +
> >  /**
> >   * group_queue_work() - Queue a group work
> >   * @group: Group to queue the work for.
> > @@ -730,6 +758,9 @@ struct panthor_job {
> >  	/** @queue_idx: Index of the queue inside @group. */
> >  	u32 queue_idx;
> >  
> > +	/** @ringbuf_idx: Index of the ringbuffer inside @queue. */
> > +	u32 ringbuf_idx;
> > +
> >  	/** @call_info: Information about the userspace command stream call. */
> >  	struct {
> >  		/** @start: GPU address of the userspace command stream. */
> > @@ -764,6 +795,9 @@ struct panthor_job {
> >  
> >  	/** @done_fence: Fence signaled when the job is finished or cancelled. */
> >  	struct dma_fence *done_fence;
> > +
> > +	/** @is_profiled: Whether timestamp and cycle numbers were gathered for this job */
> > +	bool is_profiled;
> >  };
> >  
> >  static void
> > @@ -844,7 +878,7 @@ static void group_release_work(struct work_struct *work)
> >  
> >  	panthor_kernel_bo_destroy(group->suspend_buf);
> >  	panthor_kernel_bo_destroy(group->protm_suspend_buf);
> > -	panthor_kernel_bo_destroy(group->syncobjs);
> > +	panthor_kernel_bo_destroy(group->syncobjs.bo);
> >  
> >  	panthor_vm_put(group->vm);
> >  	kfree(group);
> > @@ -1969,8 +2003,6 @@ tick_ctx_init(struct panthor_scheduler *sched,
> >  	}
> >  }
> >  
> > -#define NUM_INSTRS_PER_SLOT		16
> > -
> >  static void
> >  group_term_post_processing(struct panthor_group *group)
> >  {
> > @@ -2007,7 +2039,7 @@ group_term_post_processing(struct panthor_group *group)
> >  		spin_unlock(&queue->fence_ctx.lock);
> >  
> >  		/* Manually update the syncobj seqno to unblock waiters. */
> > -		syncobj = group->syncobjs->kmap + (i * sizeof(*syncobj));
> > +		syncobj = group->syncobjs.bo->kmap + (i * sizeof(*syncobj));
> >  		syncobj->status = ~0;
> >  		syncobj->seqno = atomic64_read(&queue->fence_ctx.seqno);
> >  		sched_queue_work(group->ptdev->scheduler, sync_upd);
> > @@ -2780,7 +2812,7 @@ static void group_sync_upd_work(struct work_struct *work)
> >  		if (!queue)
> >  			continue;
> >  
> > -		syncobj = group->syncobjs->kmap + (queue_idx * sizeof(*syncobj));
> > +		syncobj = group->syncobjs.bo->kmap + (queue_idx * sizeof(*syncobj));
> >  
> >  		spin_lock(&queue->fence_ctx.lock);
> >  		list_for_each_entry_safe(job, job_tmp, &queue->fence_ctx.in_flight_jobs, node) {
> > @@ -2815,22 +2847,81 @@ queue_run_job(struct drm_sched_job *sched_job)
> >  	struct panthor_scheduler *sched = ptdev->scheduler;
> >  	u32 ringbuf_size = panthor_kernel_bo_size(queue->ringbuf);
> >  	u32 ringbuf_insert = queue->iface.input->insert & (ringbuf_size - 1);
> > +	u32 ringbuf_index = ringbuf_insert / (SLOTSIZE);
> > +	bool ringbuf_wraparound =
> > +		job->is_profiled && ((ringbuf_size/SLOTSIZE) == ringbuf_index + 1);
> >  	u64 addr_reg = ptdev->csif_info.cs_reg_count -
> >  		       ptdev->csif_info.unpreserved_cs_reg_count;
> >  	u64 val_reg = addr_reg + 2;
> > -	u64 sync_addr = panthor_kernel_bo_gpuva(group->syncobjs) +
> > -			job->queue_idx * sizeof(struct panthor_syncobj_64b);
> > +	u64 cycle_reg = addr_reg;
> > +	u64 time_reg = val_reg;
> > +	u64 sync_addr = panthor_kernel_bo_gpuva(group->syncobjs.bo) +
> > +		job->queue_idx * sizeof(struct panthor_syncobj_64b);
> > +	u64 times_addr = panthor_kernel_bo_gpuva(group->syncobjs.bo) + queue->time_offset +
> > +		(ringbuf_index * sizeof(struct panthor_job_times));
> > +	size_t call_insrt_size;
> 
> NIT: s/insrt/instr/
> 
> > +	u64 *call_instrs;
> > +
> >  	u32 waitall_mask = GENMASK(sched->sb_slot_count - 1, 0);
> >  	struct dma_fence *done_fence;
> >  	int ret;
> >  
> > -	u64 call_instrs[NUM_INSTRS_PER_SLOT] = {
> > +	u64 call_instrs_simple[NUM_INSTRS_PER_SLOT] = {
> > +		/* MOV32 rX+2, cs.latest_flush */
> > +		(2ull << 56) | (val_reg << 48) | job->call_info.latest_flush,
> > +
> > +		/* FLUSH_CACHE2.clean_inv_all.no_wait.signal(0) rX+2 */
> > +		(36ull << 56) | (0ull << 48) | (val_reg << 40) | (0 << 16) | 0x233,
> > +
> > +		/* MOV48 rX:rX+1, cs.start */
> > +		(1ull << 56) | (addr_reg << 48) | job->call_info.start,
> > +
> > +		/* MOV32 rX+2, cs.size */
> > +		(2ull << 56) | (val_reg << 48) | job->call_info.size,
> > +
> > +		/* WAIT(0) => waits for FLUSH_CACHE2 instruction */
> > +		(3ull << 56) | (1 << 16),
> > +
> > +		/* CALL rX:rX+1, rX+2 */
> > +		(32ull << 56) | (addr_reg << 40) | (val_reg << 32),
> > +
> > +		/* MOV48 rX:rX+1, sync_addr */
> > +		(1ull << 56) | (addr_reg << 48) | sync_addr,
> > +
> > +		/* MOV48 rX+2, #1 */
> > +		(1ull << 56) | (val_reg << 48) | 1,
> > +
> > +		/* WAIT(all) */
> > +		(3ull << 56) | (waitall_mask << 16),
> > +
> > +		/* SYNC_ADD64.system_scope.propage_err.nowait rX:rX+1, rX+2*/
> > +		(51ull << 56) | (0ull << 48) | (addr_reg << 40) | (val_reg << 32) | (0 << 16) | 1,
> > +
> > +		/* ERROR_BARRIER, so we can recover from faults at job
> > +		 * boundaries.
> > +		 */
> > +		(47ull << 56),
> > +	};
> > +
> > +	u64 call_instrs_profile[NUM_INSTRS_PER_SLOT*2] = {
> >  		/* MOV32 rX+2, cs.latest_flush */
> >  		(2ull << 56) | (val_reg << 48) | job->call_info.latest_flush,
> >  
> >  		/* FLUSH_CACHE2.clean_inv_all.no_wait.signal(0) rX+2 */
> >  		(36ull << 56) | (0ull << 48) | (val_reg << 40) | (0 << 16) | 0x233,
> >  
> > +		/* MOV48 rX:rX+1, cycles_offset */
> > +		(1ull << 56) | (cycle_reg << 48) | (times_addr + offsetof(struct panthor_job_times, cycles.before)),
> > +
> > +		/* MOV48 rX:rX+1, time_offset */
> > +		(1ull << 56) | (time_reg << 48) | (times_addr + offsetof(struct panthor_job_times, time.before)),
> > +
> > +		/* STORE_STATE cycles */
> > +		(40ull << 56) |  (cycle_reg << 40) | (1ll << 32),
> > +
> > +		/* STORE_STATE timer */
> > +		(40ull << 56) |  (time_reg << 40) | (0ll << 32),
> > +
> >  		/* MOV48 rX:rX+1, cs.start */
> >  		(1ull << 56) | (addr_reg << 48) | job->call_info.start,
> >  
> > @@ -2843,6 +2934,18 @@ queue_run_job(struct drm_sched_job *sched_job)
> >  		/* CALL rX:rX+1, rX+2 */
> >  		(32ull << 56) | (addr_reg << 40) | (val_reg << 32),
> >  
> > +		/* MOV48 rX:rX+1, cycles_offset */
> > +		(1ull << 56) | (cycle_reg << 48) | (times_addr + offsetof(struct panthor_job_times, cycles.after)),
> > +
> > +		/* MOV48 rX:rX+1, time_offset */
> > +		(1ull << 56) | (time_reg << 48) | (times_addr + offsetof(struct panthor_job_times, time.after)),
> > +
> > +		/* STORE_STATE cycles */
> > +		(40ull << 56) |  (cycle_reg << 40) | (1ll << 32),
> > +
> > +		/* STORE_STATE timer */
> > +		(40ull << 56) |  (time_reg << 40) | (0ll << 32),
> > +
> >  		/* MOV48 rX:rX+1, sync_addr */
> >  		(1ull << 56) | (addr_reg << 48) | sync_addr,
> >  
> > @@ -2862,9 +2965,18 @@ queue_run_job(struct drm_sched_job *sched_job)
> >  	};
> >  
> >  	/* Need to be cacheline aligned to please the prefetcher. */
> > -	static_assert(sizeof(call_instrs) % 64 == 0,
> > +	static_assert(sizeof(call_instrs_simple) % 64 == 0 && sizeof(call_instrs_profile) % 64 == 0,
> >  		      "call_instrs is not aligned on a cacheline");
> >  
> > +	if (job->is_profiled) {
> > +		call_instrs = call_instrs_profile;
> > +		call_insrt_size = sizeof(call_instrs_profile);
> > +
> > +	} else {
> > +		call_instrs = call_instrs_simple;
> > +		call_insrt_size = sizeof(call_instrs_simple);
> > +	}
> > +
> >  	/* Stream size is zero, nothing to do => return a NULL fence and let
> >  	 * drm_sched signal the parent.
> >  	 */
> > @@ -2887,8 +2999,23 @@ queue_run_job(struct drm_sched_job *sched_job)
> >  		       queue->fence_ctx.id,
> >  		       atomic64_inc_return(&queue->fence_ctx.seqno));
> >  
> > -	memcpy(queue->ringbuf->kmap + ringbuf_insert,
> > -	       call_instrs, sizeof(call_instrs));
> > +	/*
> > +	 * Need to handle the wrap-around case when copying profiled instructions
> > +	 * from an odd-indexed slot. The reason this can happen is user space is
> > +	 * able to control the profiling status of the driver through a sysfs
> > +	 * knob, so this might lead to a timestamp and cycles-profiling call
> > +	 * instruction stream beginning at an odd-number slot. The GPU should
> > +	 * be able to gracefully handle this.
> > +	 */
> > +	if (!ringbuf_wraparound) {
> > +		memcpy(queue->ringbuf->kmap + ringbuf_insert,
> > +		       call_instrs, call_insrt_size);
> > +	} else {
> > +		memcpy(queue->ringbuf->kmap + ringbuf_insert,
> > +		       call_instrs, call_insrt_size/2);
> > +		memcpy(queue->ringbuf->kmap, call_instrs +
> > +		       NUM_INSTRS_PER_SLOT, call_insrt_size/2);
> > +	}
> 
> A minor point, but I think it would just be easier to always do the copy
> in two parts:
> 
> 	memcpy(queue->ringbuf->kmap + ringbuf_insert,
> 	       call_instrs, NUM_INSTRS_PER_SLOT);
> 	if (profiling) {
> 		ringbuf_insert += NUM_INSTRS_PER_SLOT;
> 		ringbuf_insert &= (ringbuf_size - 1);
> 		memcpy(queue->ringbuf->kmap + ringbuf_insert,
> 		       call_instrs + NUM_INSTRS_PER_SLOT,
> 		       NUM_INSTRS_PER_SLOT);
> 	}
> 
> >  
> >  	panthor_job_get(&job->base);
> >  	spin_lock(&queue->fence_ctx.lock);
> > @@ -2896,7 +3023,8 @@ queue_run_job(struct drm_sched_job *sched_job)
> >  	spin_unlock(&queue->fence_ctx.lock);
> >  
> >  	job->ringbuf.start = queue->iface.input->insert;
> > -	job->ringbuf.end = job->ringbuf.start + sizeof(call_instrs);
> > +	job->ringbuf.end = job->ringbuf.start + call_insrt_size;
> > +	job->ringbuf_idx = ringbuf_index;
> >  
> >  	/* Make sure the ring buffer is updated before the INSERT
> >  	 * register.
> > @@ -2987,7 +3115,8 @@ static const struct drm_sched_backend_ops panthor_queue_sched_ops = {
> >  
> >  static struct panthor_queue *
> >  group_create_queue(struct panthor_group *group,
> > -		   const struct drm_panthor_queue_create *args)
> > +		   const struct drm_panthor_queue_create *args,
> > +		   unsigned int slots_so_far)
> 
> I'm not sure I like the name "slots_so_far", "slot_offset" maybe?
> Although my main gripe is below...

I agree, that would be better naming.

> >  {
> >  	struct drm_gpu_scheduler *drm_sched;
> >  	struct panthor_queue *queue;
> > @@ -3038,9 +3167,17 @@ group_create_queue(struct panthor_group *group,
> >  		goto err_free_queue;
> >  	}
> >  
> > +	queue->time_offset = group->syncobjs.job_times_offset +
> > +		(slots_so_far * sizeof(struct panthor_job_times));
> > +
> > +	/*
> > +	 * Credit limit argument tells us the total number of instructions
> > +	 * across all CS slots in the ringbuffer, with some jobs requiring
> > +	 * twice as many as others, depending on their profiling status.
> > +	 */
> >  	ret = drm_sched_init(&queue->scheduler, &panthor_queue_sched_ops,
> >  			     group->ptdev->scheduler->wq, 1,
> > -			     args->ringbuf_size / (NUM_INSTRS_PER_SLOT * sizeof(u64)),
> > +			     args->ringbuf_size / sizeof(u64),
> >  			     0, msecs_to_jiffies(JOB_TIMEOUT_MS),
> >  			     group->ptdev->reset.wq,
> >  			     NULL, "panthor-queue", group->ptdev->base.dev);
> > @@ -3068,7 +3205,9 @@ int panthor_group_create(struct panthor_file *pfile,
> >  	struct panthor_scheduler *sched = ptdev->scheduler;
> >  	struct panthor_fw_csg_iface *csg_iface = panthor_fw_get_csg_iface(ptdev, 0);
> >  	struct panthor_group *group = NULL;
> > +	unsigned int total_slots;
> >  	u32 gid, i, suspend_size;
> > +	size_t syncobj_bo_size;
> >  	int ret;
> >  
> >  	if (group_args->pad)
> > @@ -3134,33 +3273,75 @@ int panthor_group_create(struct panthor_file *pfile,
> >  		goto err_put_group;
> >  	}
> >  
> > -	group->syncobjs = panthor_kernel_bo_create(ptdev, group->vm,
> > -						   group_args->queues.count *
> > -						   sizeof(struct panthor_syncobj_64b),
> > -						   DRM_PANTHOR_BO_NO_MMAP,
> > -						   DRM_PANTHOR_VM_BIND_OP_MAP_NOEXEC |
> > -						   DRM_PANTHOR_VM_BIND_OP_MAP_UNCACHED,
> > -						   PANTHOR_VM_KERNEL_AUTO_VA);
> > -	if (IS_ERR(group->syncobjs)) {
> > -		ret = PTR_ERR(group->syncobjs);
> > +	/*
> > +	 * Need to add size for the panthor_job_times structs, as many as the sum
> > +	 * of the number of job slots for every single queue ringbuffer.
> > +	 */
> > +	for (i = 0, total_slots = 0; i < group_args->queues.count; i++)
> > +		total_slots += (queue_args[i].ringbuf_size / (SLOTSIZE));
> > +
> > +	syncobj_bo_size = (group_args->queues.count * sizeof(struct panthor_syncobj_64b))
> > +		+ (total_slots * sizeof(struct panthor_job_times));
> > +
> > +	/*
> > +	 * Memory layout of group's syncobjs BO
> > +	 * group->syncobjs.bo {
> > +	 *	struct panthor_syncobj_64b sync1;
> > +	 *	struct panthor_syncobj_64b sync2;
> > +	 *		...
> > +	 *		As many as group_args->queues.count
> > +	 *		...
> > +	 *	struct panthor_syncobj_64b syncn;
> > +	 *	struct panthor_job_times queue1_slot1
> > +	 *	struct panthor_job_times queue1_slot2
> > +	 *		...
> > +	 *		As many as queue[i].ringbuf_size / SLOTSIZE
> > +	 *		...
> > +	 *	struct panthor_job_times queue1_slotP
> > +	 *		...
> > +	 *		As many as group_args->queues.count
> > +	 *		...
> > +	 *	struct panthor_job_times queueN_slot1
> > +	 *	struct panthor_job_times queueN_slot2
> > +	 *		...
> > +	 *		As many as queue[n].ringbuf_size / SLOTSIZE
> > +	 *	struct panthor_job_times queueN_slotQ
> > +	 *
> > +	 *	Linearly, group->syncobjs.bo = {syncojb1,..,syncobjN,
> > +	 *	{queue1 = {js1,..,jsP},..,queueN = {js1,..,jsQ}}}
> > +	 * }
> > +	 *
> > +	 */
> > +
> > +	group->syncobjs.bo = panthor_kernel_bo_create(ptdev, group->vm,
> > +						      syncobj_bo_size,
> > +						      DRM_PANTHOR_BO_NO_MMAP,
> > +						      DRM_PANTHOR_VM_BIND_OP_MAP_NOEXEC |
> > +						      DRM_PANTHOR_VM_BIND_OP_MAP_UNCACHED,
> > +						      PANTHOR_VM_KERNEL_AUTO_VA);
> > +	if (IS_ERR(group->syncobjs.bo)) {
> > +		ret = PTR_ERR(group->syncobjs.bo);
> >  		goto err_put_group;
> >  	}
> >  
> > -	ret = panthor_kernel_bo_vmap(group->syncobjs);
> > +	ret = panthor_kernel_bo_vmap(group->syncobjs.bo);
> >  	if (ret)
> >  		goto err_put_group;
> >  
> > -	memset(group->syncobjs->kmap, 0,
> > -	       group_args->queues.count * sizeof(struct panthor_syncobj_64b));
> > +	memset(group->syncobjs.bo->kmap, 0, syncobj_bo_size);
> >  
> > -	for (i = 0; i < group_args->queues.count; i++) {
> > -		group->queues[i] = group_create_queue(group, &queue_args[i]);
> > +	group->syncobjs.job_times_offset =
> > +		group_args->queues.count * sizeof(struct panthor_syncobj_64b);
> > +
> > +	for (i = 0, total_slots = 0; i < group_args->queues.count; i++) {
> 
> I definitely don't like this usage of total_slots. Here "slots_so_far"
> would be a better name (which would justify the parameter name avoid),
> and would avoid the confusion that total_slots already had a value
> (which was indeed the total slots) but is now being reused for a running
> counter.

I agree, I'll change the naming in the next revision.

> Steve
> 
> > +		group->queues[i] = group_create_queue(group, &queue_args[i], total_slots);
> >  		if (IS_ERR(group->queues[i])) {
> >  			ret = PTR_ERR(group->queues[i]);
> >  			group->queues[i] = NULL;
> >  			goto err_put_group;
> >  		}
> >  
> > +		total_slots += (queue_args[i].ringbuf_size / (SLOTSIZE));
> >  		group->queue_count++;
> >  	}
> >  
> > @@ -3384,9 +3565,12 @@ panthor_job_create(struct panthor_file *pfile,
> >  		goto err_put_job;
> >  	}
> >  
> > +	job->is_profiled = pfile->ptdev->profile_mode;
> > +
> >  	ret = drm_sched_job_init(&job->base,
> >  				 &job->group->queues[job->queue_idx]->entity,
> > -				 1, job->group);
> > +				 job->is_profiled ? NUM_INSTRS_PER_SLOT * 2 :
> > +				 NUM_INSTRS_PER_SLOT, job->group);
> 
> Is there a good reason to make the credits the number of instructions,
> rather than the number of slots? If we were going to count the actual
> number of non-NOP instructions then there would be some logic (although
> I'm not convinced that makes much sense), but considering we only allow
> submission in "slot granules" we might as well use that as the unit of
> "credit".

In my initial pre-ML version of the patch series I was passing the number of
queue slots as the total credit count, but Boris was keener on setting it to
the total number of instructions instead.

I agree with you that both are equivalent, one just being an integer multiple
of the other, so I'm fine with either choice. Maybe Boris can pitch in, in
case he has a strong opinion about this.

> Steve
> 
> >  	if (ret)
> >  		goto err_put_job;
> >  

Adrian Larumbe