[Bug 98815] [SKL/BDW GT2]  large perf regression in TessMark

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Nov 22 12:24:49 UTC 2016


https://bugs.freedesktop.org/show_bug.cgi?id=98815

            Bug ID: 98815
           Summary: [SKL/BDW GT2] large perf regression in TessMark
           Product: Mesa
           Version: git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Drivers/DRI/i965
          Assignee: intel-3d-bugs at lists.freedesktop.org
          Reporter: eero.t.tamminen at intel.com
        QA Contact: intel-3d-bugs at lists.freedesktop.org

Setup:
- SKL i5 GT2 (i5-6600K + 2x 2400Mhz DDR4)
- Ubuntu 16.04
- Mesa from Git
- GpuTest v0.7: http://www.geeks3d.com/gputest/download/


Test-case:
MESA_GL_VERSION_OVERRIDE=4.0 ./GpuTest /test=tess_x64 /width=1366 /height=768
/benchmark

(Test-case fails with Mesa unless one overrides it with some GL 4.x version.)


Following commit drops TessMark x64 performance considerably:
-------------------------------------------------------
commit 6d416bcd846a49414f210cd761789156c37a7b3e
Author:     Kenneth Graunke <kenneth at whitecape.org>
AuthorDate: Tue Nov 15 01:03:13 2016 -0800
Commit:     Kenneth Graunke <kenneth at whitecape.org>
CommitDate: Sat Nov 19 11:40:00 2016 -0800

    i965: Use arrays in Gen7+ URB code.

    So much of this code was cut and pasted per stage.  We can accomplish
    much of it by looping over shader stages.

    Improves performance of OglBatch7 (version 6) by 1.50783% +/- 0.287049%
    (n = 71) at 1024x768 on Cherryview.

    Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
    Reviewed-by: Topi Pohjolainen <topi.pohjolainen at intel.com>
-------------------------------------------------------

On SKL GT2, drop is ~17% in FullHD fullscreen and increases when the window
size decreases.  With 1/2 FullHD window, the drop is ~27%.

Drop is visible also on BDW GT2, but it's clearly smaller.  I don't see drop on
BDW GT3, BSW, or on edram machines (HSW GT3e, SKL GT3e, SKL GT4e).

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