[Intel-xe] [PATCH] drm/xe: Use large rings for compute contexts

[Thomas Hellström]

Hi, Niranjana,

On 6/2/23 20:07, Niranjana Vishwanathapura wrote:
> Allow compute contexts to submit the maximal amount of work without
> blocking userspace.
>
> The original size for user LRC ring's (SZ_16K) was chosen to minimise
> memory consumption, without being so small as to frequently stall in the
> middle of workloads. With the main consumers being GL / media pipelines
> of 2 or 3 batches per frame, we want to support ~10 requests in flight
> to allow for the application to control throttling without stalling
> within a frame.
>
> Signed-off-by: Chris Wilson <chris.p.wilson at intel.com>
> Signed-off-by: Tejas Upadhyay <tejas.upadhyay at intel.com>
> Signed-off-by: Andi Shyti <andi.shyti at linux.intel.com>
> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>

With the DRM scheduler, jobs are written to the ring from a drm 
scheduler notifier when all dependencies are satisfied and there is ring 
space available, and I believe that's the case even after Matthew 
Brost's changes to xe / drm-scheduler on how compute jobs are handled.

So this patch shouldn't be needed for xe.

/Thomas

> ---
>   drivers/gpu/drm/xe/xe_engine.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_engine.c b/drivers/gpu/drm/xe/xe_engine.c
> index b3036c4a8ec3..47c9f119fb29 100644
> --- a/drivers/gpu/drm/xe/xe_engine.c
> +++ b/drivers/gpu/drm/xe/xe_engine.c
> @@ -29,6 +29,7 @@ static struct xe_engine *__xe_engine_create(struct xe_device *xe,
>   {
>   	struct xe_engine *e;
>   	struct xe_gt *gt = hwe->gt;
> +	u32 ring_size;
>   	int err;
>   	int i;
>   
> @@ -65,8 +66,9 @@ static struct xe_engine *__xe_engine_create(struct xe_device *xe,
>   		e->bind.fence_seqno = XE_FENCE_INITIAL_SEQNO;
>   	}
>   
> +	ring_size = (e->class == XE_ENGINE_CLASS_COMPUTE) ? SZ_512K : SZ_16K;
>   	for (i = 0; i < width; ++i) {
> -		err = xe_lrc_init(e->lrc + i, hwe, e, vm, SZ_16K);
> +		err = xe_lrc_init(e->lrc + i, hwe, e, vm, ring_size);
>   		if (err)
>   			goto err_lrc;
>   	}