[Bug 108888] [CI][SHARDS] igt at gem_exec_fence@basic-await-default - fail - Failed assertion: out[n] == 0

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108888

Chris Wilson <chris at chris-wilson.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #3 from Chris Wilson <chris at chris-wilson.co.uk> ---
Haswell is no longer the odd one out,

commit 6faf5916e6beb0dedb0fcbbafbaa152adeaea758
Author: Chris Wilson <chris at chris-wilson.co.uk>
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: https://bugs.freedesktop.org/show_bug.cgi?id=108888
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Reviewed-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
    Link:
https://patchwork.freedesktop.org/patch/msgid/20181228140736.32606-2-chris@chris-wilson.co.uk

-- 
You are receiving this mail because:
You are the QA Contact for the bug.
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/intel-gfx-bugs/attachments/20181228/60ec09a7/attachment.html>