[Intel-gfx] [PATCH 0/4] prevent stalls due to tiling changes and bo reuse

[Daniel Vetter]

Hi all,

This patch-set prevents stalls due to bo reuse in libdrm. After having
tried to fix the set_tiling stall both in libdrm and the kernel, I think
fixing this in the kernel is the better option: This way gem nicely
abstracts away the execution semantics. The only place where the
asynchronous nature of the gpu leaks is in the busy ioctl, which userspace
should call to check whether a mmap of the bo would stall.

Performance gains are minimal, but strictly positive (neglecting a 1% noise
level).  cairo perf traces on my i945:

old: without-patches
new: with-patches
Speedups
========
 xlib-rgba       firefox-planet-gnome-0    62418.67 (64895.61 1.98%) -> 57833.66
 (61105.65 2.92%):  1.08x speedup

A few traces more have small speedups ranging 1%-5%.

I expect this to perform better when all the other tiling related problems
are fixed - unfortunately I can't benchmark this because fixing tiling needs
portions of my pipelined fencing work (the exact fence lru accounting),
which is not (yet) ported to current drm-next.

Please review and consider merging for -next. Patches apply to current
drm-next.

Thanks, Daniel

Daniel Vetter (4):
  drm/i915: don't allow tiling changes on pinned buffers
  drm/i915: introduce i915_gem_object_adjust_fencing
  drm/i915: adjust fence register asynchronously on tiling changes
  drm/i915: report all active objects as busy

 drivers/gpu/drm/i915/i915_drv.h        |    8 +++-
 drivers/gpu/drm/i915/i915_gem.c        |   88 ++++++++++++++++++++++++++------
 drivers/gpu/drm/i915/i915_gem_tiling.c |   29 +++-------
 drivers/gpu/drm/i915/intel_display.c   |   16 ++----
 4 files changed, 92 insertions(+), 49 deletions(-)