<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_RESOLVED bz_closed" title="RESOLVED FIXED - [CI][SHARDS] igt@gem_exec_fence@basic-await-default - fail - Failed assertion: out[n] == 0" href="https://bugs.freedesktop.org/show_bug.cgi?id=108888#c5">Comment # 5</a> on <a class="bz_bug_link bz_status_RESOLVED bz_closed" title="RESOLVED FIXED - [CI][SHARDS] igt@gem_exec_fence@basic-await-default - fail - Failed assertion: out[n] == 0" href="https://bugs.freedesktop.org/show_bug.cgi?id=108888">bug 108888</a> from <a class="email" href="mailto:martin.peres@free.fr" title="Martin Peres <martin.peres@free.fr>"> Martin Peres</a> <pre>(In reply to Chris Wilson from <a href="show_bug.cgi?id=108888#c3">comment #3</a>) > Haswell is no longer the odd one out, > > commit 6faf5916e6beb0dedb0fcbbafbaa152adeaea758 > Author: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>> > Date: Fri Dec 28 14:07:35 2018 +0000 > > drm/i915: Remove HW semaphores for gen7 inter-engine synchronisation > > The writing is on the wall for the existence of a single execution queue > along each engine, and as a consequence we will not be able to track > dependencies along the HW queue itself, i.e. we will not be able to use > HW semaphores on gen7 as they use a global set of registers (and unlike > gen8+ we can not effectively target memory to keep per-context seqno and > dependencies). > > On the positive side, when we implement request reordering for gen7 we > also can not presume a simple execution queue and would also require > removing the current semaphore generation code. So this bring us another > step closer to request reordering for ringbuffer submission! > > The negative side is that using interrupts to drive inter-engine > synchronisation is much slower (4us -> 15us to do a nop on each of the 3 > engines on ivb). This is much better than it was at the time of > introducing > the HW semaphores and equally important userspace weaned itself off > intermixing dependent BLT/RENDER operations (the prime culprit was glyph > rendering in UXA). So while we regress the microbenchmarks, it should not > impact the user. > > References: <a class="bz_bug_link bz_status_RESOLVED bz_closed" title="RESOLVED FIXED - [CI][SHARDS] igt@gem_exec_fence@basic-await-default - fail - Failed assertion: out[n] == 0" href="show_bug.cgi?id=108888">https://bugs.freedesktop.org/show_bug.cgi?id=108888</a> > Signed-off-by: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>> > Reviewed-by: Mika Kuoppala <<a href="mailto:mika.kuoppala@linux.intel.com">mika.kuoppala@linux.intel.com</a>> > Link: > <a href="https://patchwork.freedesktop.org/patch/msgid/20181228140736.32606-2">https://patchwork.freedesktop.org/patch/msgid/20181228140736.32606-2</a>- > <a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a> Thanks! Let's hope it fixes the IVB and BYT issues too (which are also gen7). So far, it's been only 2 drmtip runs since this patch landed but the reproduction rate was quite sporadic, so I guess we'll have to be a little patient.</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> <li>You are on the CC list for the bug.</li> </ul> </body> </html>