[Bug 103940] 1% perf drop in SynMark PSPom test from "intel/fs: Be more explicit about our placement of [un]zip"

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Mon Nov 27 15:47:09 UTC 2017


            Bug ID: 103940
           Summary: 1% perf drop in SynMark PSPom test from "intel/fs: Be
                    more explicit about our placement of [un]zip"
           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

Following commit was bisected (on SKL GT2):
commit 0d905597fe2997c89022c76cdf84dc4fba5eb055
Author:     Jason Ekstrand <jason.ekstrand at intel.com>
AuthorDate: Wed Sep 6 18:31:11 2017 -0700
Commit:     Jason Ekstrand <jason.ekstrand at intel.com>
CommitDate: Tue Nov 7 10:37:52 2017 -0800

    intel/fs: Be more explicit about our placement of [un]zip

    Before, we were careful to place the zip after the last of the split
    instructions but did unzip on-demand.  This changes things so that the
    unzips go before all of the split instructions and the unzip comes
    explicitly after all the split instructions.  As a side-effect of this
    change, we now emit the split instruction from highest SIMD group to
    lowest instead of low to high.  We could have kept the old behavior, but
    it shouldn't matter and this made the code easier.

    Reviewed-by: Iago Toral Quiroga <itoral at igalia.com>
    Cc: mesa-stable at lists.freedesktop.org

To be the cause for the SynMark v7 PSPom drop visible on following platforms:
* 2% in BXT J4205, KBL GT3e
* 1-2% on BSW N3050
* 1% on BDW GT2, SKL GT2 & GT4e

This test didn't improve on any other platform and no other test was affected.

(I'm OK if this is closed as WONTFIX, I filed this more to document the perf

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