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

[Niranjana Vishwanathapura]

On Mon, Jun 05, 2023 at 10:33:29AM +0200, Thomas Hellström wrote:
>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.
>

Ok, got it, thanks.

Niranjana

>/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;
>>  	}