On Thu, Apr 07, 2022 at 04:16:27PM +0100, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
>
> Inherit submitter nice at point of request submission to account for long
> running processes getting either externally or self re-niced.
>
> This accounts for the current processing landscape where computational
> pipelines are composed of CPU and GPU parts working in tandem.
>
> Nice value will only apply to requests which originate from user contexts
> and have default context priority. This is to avoid disturbing any
> application made choices of low and high (batch processing and latency
> sensitive compositing). In this case nice value adjusts the effective
> priority in the narrow band of -19 to +20 around
> I915_CONTEXT_DEFAULT_PRIORITY.
>
> This means that userspace using the context priority uapi directly has a
> wider range of possible adjustments (in practice that only applies to
> execlists platforms - with GuC there are only three priority buckets), but
> in all cases nice adjustment has the expected effect: positive nice
> lowering the scheduling priority and negative nice raising it.
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
I don't think adding any more fancy features to i915-scheduler makes
sense, at least not before we've cut over to drm/sched.
-Daniel
> ---
> drivers/gpu/drm/i915/i915_request.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> index 582770360ad1..e5cfa073d8f0 100644
> --- a/drivers/gpu/drm/i915/i915_request.c
> +++ b/drivers/gpu/drm/i915/i915_request.c
> @@ -1811,8 +1811,17 @@ void i915_request_add(struct i915_request *rq)
> /* XXX placeholder for selftests */
> rcu_read_lock();
> ctx = rcu_dereference(rq->context->gem_context);
> - if (ctx)
> + if (ctx) {
> attr = ctx->sched;
> + /*
> + * Inherit process nice when scheduling user contexts but only
> + * if context has the default priority to avoid touching
> + * contexts where GEM uapi has been used to explicitly lower
> + * or elevate it.
> + */
> + if (attr.priority == I915_CONTEXT_DEFAULT_PRIORITY)
> + attr.priority = -task_nice(current);
> + }
> rcu_read_unlock();
>
> __i915_request_queue(rq, &attr);
> --
> 2.32.0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
