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<body><span class="vcard"><a class="email" href="mailto:martin.peres@free.fr" title="Martin Peres <martin.peres@free.fr>"> <span class="fn">Martin Peres</span></a>
</span> changed
<a class="bz_bug_link
bz_status_CLOSED bz_closed"
title="CLOSED WORKSFORME - [CI][SHARDS] igt@gem_busy@extended-semaphore-blt - fail - Failed assertion: read == active"
href="https://bugs.freedesktop.org/show_bug.cgi?id=109119">bug 109119</a>
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<tr>
<th>What</th>
<th>Removed</th>
<th>Added</th>
</tr>
<tr>
<td style="text-align:right;">Status</td>
<td>RESOLVED
</td>
<td>CLOSED
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<b><a class="bz_bug_link
bz_status_CLOSED bz_closed"
title="CLOSED WORKSFORME - [CI][SHARDS] igt@gem_busy@extended-semaphore-blt - fail - Failed assertion: read == active"
href="https://bugs.freedesktop.org/show_bug.cgi?id=109119#c3">Comment # 3</a>
on <a class="bz_bug_link
bz_status_CLOSED bz_closed"
title="CLOSED WORKSFORME - [CI][SHARDS] igt@gem_busy@extended-semaphore-blt - fail - Failed assertion: read == active"
href="https://bugs.freedesktop.org/show_bug.cgi?id=109119">bug 109119</a>
from <span class="vcard"><a class="email" href="mailto:martin.peres@free.fr" title="Martin Peres <martin.peres@free.fr>"> <span class="fn">Martin Peres</span></a>
</span></b>
<pre>(In reply to Chris Wilson from <a href="show_bug.cgi?id=109119#c2">comment #2</a>)
<span class="quote">> Tests are defunct since
>
> 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></span >
Thanks!</pre>
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