[PATCH 0/4] drm/atomic: Lockless blocking commits

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

I've talked about making blocking commits lockless a few
times in the past, so here's finally an attempt at it.
The main benefit I see from this is that TEST_ONLY commits
no longer getting blocked on the mutexes by parallel blocking
commits.

I have a small test here that spools up two threads,
one does just TEST_ONLY commits in a loop, the other
does either blocking or non-blocking page flips. Results
came out as follows on a snb machine here:

test-only-vs-non-blocking:
-85319 TEST_ONLY commits in 2000000 usecs, 23 usecs / commit
+87144 TEST_ONLY commits in 2000006 usecs, 22 usecs / commit

test-only-vs-blocking:
-219 TEST_ONLY commits in 2001768 usecs, 9140 usecs / commit
+82442 TEST_ONLY commits in 2000011 usecs, 24 usecs / commit

Now, I have no idea if anyone actually cares about lack
of parallelism due to locked blocking commits or not. Hence
Cc'd some compositor folks as well. I guess this is more of
an RFC at this point.

Also curious to see if CI goes up in smoke or not...

Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Rob Clark <robdclark at gmail.com>
Cc: Simon Ser <contact at emersion.fr>
Cc: Pekka Paalanen <pekka.paalanen at collabora.com>
Cc: Jonas Ådahl <jadahl at gmail.com>

Ville Syrjälä (4):
  drm/atomic: Treat a nonblocking commit following a blocking commit as
    blocking commit
  drm/i915: Don't reuse commit_work for the cleanup
  drm/atomic: Allow lockless blocking commits
  drm/i915: Make blocking commits lockless

 drivers/gpu/drm/drm_atomic.c                  | 32 +++++++++++++++++--
 drivers/gpu/drm/drm_atomic_helper.c           | 19 +++++++----
 drivers/gpu/drm/drm_atomic_uapi.c             | 11 +++++--
 drivers/gpu/drm/i915/display/intel_display.c  | 15 +++------
 .../drm/i915/display/intel_display_types.h    |  1 +
 include/drm/drm_atomic.h                      |  8 +++++
 6 files changed, 64 insertions(+), 22 deletions(-)

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2.35.1