[Bug 99256] [KBL] 60% perf drop in GfxBench Manhattan 3.1 with "i965/fs: Switch to the constant cache for uniform pull constants"

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99256

            Bug ID: 99256
           Summary: [KBL] 60% perf drop in GfxBench Manhattan 3.1 with
                    "i965/fs: Switch to the constant cache for uniform
                    pull constants"
           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

While Francisco's constant cache patch series helped perf on the other
platforms, *on KBL* (i7-7500U / GT2) it caused a huge perf regression in
(GfxBench 4.0) Manhattan 3.1.

"i965/fs: Switch to the constant cache for uniform pull constants" commit drops
the performance by 60% and "i965/fs: Fetch one cacheline of pull constants at a
time" commit improves that by 50%, so the combined drop is ~40%.

GfxBench CarChase (gl_4 test) test perf also dropped a bit, by 10-15%.

Note: SynMark ShMapPcf test still improved on KBL, by ~30% (same as on SKL GT2
& GT4e).

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