[Bug 102258] Up to 20% perf drop in texture sampling tests with "i965/surface_state: Get the aux usage from the miptree code"

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=102258

            Bug ID: 102258
           Summary: Up to 20% perf drop in texture sampling tests with
                    "i965/surface_state: Get the aux usage from the
                    miptree code"
           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

Bisecting on SKL GT2 revealed following commit:
----------------------------------------------------
commit dd75edb42982c1420168d509a7589032f7ead289
Author:     Jason Ekstrand <jason.ekstrand at intel.com>
AuthorDate: Wed Jun 21 21:23:20 2017 -0700
Commit:     Jason Ekstrand <jason.ekstrand at intel.com>
CommitDate: Sat Jul 22 20:59:22 2017 -0700

    i965/surface_state: Get the aux usage from the miptree code

    Reviewed-by: Topi Pohjolainen <topi.pohjolainen at intel.com>
----------------------------------------------------

To be responsible for following SKL GT2 performance drops:
- 8% in SynMark v7 TexFilterTri
- 5% in GfxBench v4 ALU2 (both onscreen & offscreen)
- 2% in SynMark v7 TexMem*
- 1% in SynMark v7 TexFilterAniso

(Tests are run in FullHD fullscreen.)

On BXT and SKL GT4e the drop is even larger, 15-20% on the filtering tests (and
10% in texture memory tests on SKL GT4e).

Note: I don't understand how surface handling changes can have that large
impact on the GfxBench ALU2 test.  Although it does do some texture accesses,
it should be ALU bound (and on BXT would greatly benefit from SIMD32).

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