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<b><a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED - [BDW Bisected] OglDrvCtx performance reduced by ~30% after use true PPGTT in Gen8+"
href="https://bugs.freedesktop.org/show_bug.cgi?id=87726#c12">Comment # 12</a>
on <a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED - [BDW Bisected] OglDrvCtx performance reduced by ~30% after use true PPGTT in Gen8+"
href="https://bugs.freedesktop.org/show_bug.cgi?id=87726">bug 87726</a>
from <span class="vcard"><a class="email" href="mailto:eero.t.tamminen@intel.com" title="Eero Tamminen <eero.t.tamminen@intel.com>"> <span class="fn">Eero Tamminen</span></a>
</span></b>
<pre>(In reply to Chris Wilson from <a href="show_bug.cgi?id=87726#c11">comment #11</a>)
<span class="quote">> From recollection, OglDrvCtx had perf regressions (and distinct
> rate-limiting steps) in mesa, dri[2,3] and the kernel.</span >
And when run for longer time, also in Unity/compiz (Ubuntu bug tracker has bug
for per-window resource leak which was opened many years ago and still
unfixed).
<span class="quote">> It was basically a glClear benchmark across lots of contexts,
> which in many respects shows the same characteristics as lots of clients.</span >
It creates a context, compiles a most trivial shader program, does color buffer
clear, and draws single triangle, swaps it on screen and deletes shaders &
context, on every frame. There's only single context live at any given time
i.e. it simulates lot of successive (windowed & composited) clients, not
parallel ones.
Because it's most trivial use-case possible, and window is fairly small, it's
only partly memory bandwidth (clear) bound.
<span class="quote">> That is a level of integration testing above igt.
> Showing the scaling characteristics of the kernel wrt to
> the number of contexts (be they one fd or many) does have coverage in igt.</span >
If you don't think relevant parts of that test couldn't be added to igt, but
you think it's still useful, I think there should be some other open source
implementation for that kind of "stress" test (it should not be left for old
version of Intel *internal* test-suite).
PS. Something I forgot to say earlier. As we aren't anymore tracking this, I
don't know who will verify the fix.</pre>
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