On Mon, Feb 13, 2017 at 01:06:42PM +0000, Tvrtko Ursulin wrote: > From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > > This removes the usage of intel_ring_emit in favour of > directly writing to the ring buffer. > > intel_ring_emit was preventing the compiler for optimising > fetch and increment of the current ring buffer pointer and > therefore generating very verbose code for every write. > > It had no useful purpose since all ringbuffer operations > are started and ended with intel_ring_begin and > intel_ring_advance respectively, with no bail out in the > middle possible, so it is fine to increment the tail in > intel_ring_begin and let the code manage the pointer > itself. > > Useless instruction removal amounts to approximately > two and half kilobytes of saved text on my build. > > Not sure if this has any measurable performance > implications but executing a ton of useless instructions > on fast paths cannot be good. > > Patch is not fully polished, but it compiles and runs > on Gen9 at least. > > v2: > * Change return from intel_ring_begin to error pointer by > popular demand. > * Move tail increment to intel_ring_advance to enable some > error checking. > > v3: > * Move tail advance back into intel_ring_begin. > * Rebase and tidy. > > v4: > * Complete rebase after a few months since v3. > > v5: > * Remove unecessary cast and fix !debug compile. (Chris Wilson) > > v6: > * Make intel_ring_offset take request as well. > * Fix recording of request postfix plus a sprinkle of asserts. > (Chris Wilson) > > v7: > * Use intel_ring_offset to get the postfix. (Chris Wilson) > * Convert GVT code as well. > > v8: > * Rename *out++ to *cs++. > > v9: > * Fix GVT out to cs conversion in GVT. Lgtm, just to warn you I've added a new intel_ring_begin in drivers/gpu/drm/i915/selftests/i915_gem_coherency.c > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx> > Cc: Zhi Wang <zhi.a.wang@xxxxxxxxx> > Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> (v7) Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
