[Intel-gfx] [PATCH 06/37] drm/i915: Move rate-limiting request retire to after submission

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-06-29 11:00:30)
> 
> On 29/06/2018 08:53, Chris Wilson wrote:
> > Our long standing defense against a single client from flooding the
> > system with requests (causing mempressure and stalls across the whole
> > system) is to retire the old request on every allocation. (By retiring
> > the oldest, we try to keep returning requests back to the system in a
> > steady flow.) This adds an extra step into the submission path that we
> > can reduce simply by moving it to after the submission itself.
> > 
> > We already do try to clean up a stale request list after submission, so
> > always retiring all completed requests fits in as a natural extension.
> 
> Please add to the commit message what motivated you to do this. Like 
> this benchmark, or something, is now better in this or that respect. Or 
> something.

This was mentioned in

commit 9512f985c32d45ab439a210981e0d73071da395a
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Thu Jun 28 21:12:11 2018 +0100

    drm/i915/execlists: Direct submission of new requests (avoid tasklet/ksoftirqd)
-Chris