Bug 104163

Summary: [GEN9+] 2-3% perf drop in GfxBench Manhattan 3.1 from "i965: Disable regular fast-clears (CCS_D) on gen9+"
Product: Mesa Reporter: Eero Tamminen <eero.t.tamminen>
Component: Drivers/DRI/i965Assignee: Intel 3D Bugs Mailing List <intel-3d-bugs>
Status: VERIFIED FIXED QA Contact: Intel 3D Bugs Mailing List <intel-3d-bugs>
Severity: normal    
Priority: medium    
Version: git   
Hardware: Other   
OS: All   
See Also: https://bugs.freedesktop.org/show_bug.cgi?id=102435
Whiteboard:
i915 platform: i915 features:

Description Eero Tamminen 2017-12-07 13:24:29 UTC 
This commit:
----------------------------------------------------
commit ee57b15ec764736e2d5360beaef9fb2045ed0f68
Author:     Jason Ekstrand <jason.ekstrand@intel.com>
AuthorDate: Wed Nov 29 16:22:42 2017 -0800
Commit:     Jason Ekstrand <jason.ekstrand@intel.com>
CommitDate: Fri Dec 1 10:14:28 2017 -0800

    i965: Disable regular fast-clears (CCS_D) on gen9+
    
    This partially reverts commit 3e57e9494c2279580ad6a83ab8c065d01e7e634e
    which caused a bunch of GPU hangs on several Source titles.  To date, we
    have no clue why these hangs are actually happening.  This undoes the
    final effect of 3e57e9494c227 and gets us back to not hanging.  Tested
    with Team Fortress 2.
    
    Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102435
    Fixes: 3e57e9494c2279580ad6a83ab8c065d01e7e634e
    Cc: mesa-stable@lists.freedesktop.org
----------------------------------------------------

Causes following performance drops on GEN9+ (Core) platforms:
* 2-3% in GfxBench Manhattan 3.1
* 1-2% in GfxBench CarChase, SynMark v7 Deferred
* 1% in GfxBench Aztec Ruins

Only other affected test was less relevant / partly CPU bound SynMark DrvState, it improved by 2% (because it has large number of small viewports which cause fast-clear handling CPU overhead affect it more than memory bandwidth).

I don't have yet data from BXT, but on GLK the impact was smaller.
Comment 1 Jason Ekstrand 2018-01-17 05:42:41 UTC 
This should all be fixed by the following commit:

commit f79bb2e651f329364dfb3db0aac4b72f91f130cc
Author: Jason Ekstrand <jason.ekstrand@intel.com>
Date:   Tue Dec 5 14:41:48 2017 -0800

    Re-enable regular fast-clears (CCS_D) on gen9+
    
    This reverts commit ee57b15ec764736e2d5360beaef9fb2045ed0f68, "i965:
    Disable regular fast-clears (CCS_D) on gen9+".  How taht we've fixed the
    issue with too many different aux usages in the render cache, it should
    be safe to re-enable CCS_D for sRGB.
    
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104163
    Tested-by: Eero Tamminen <eero.t.tamminen@intel.com>
    Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
    Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
    Cc: "17.3" <mesa-stable@lists.freedesktop.org>
Comment 2 Eero Tamminen 2018-12-05 11:55:00 UTC 
Forgot to update this when I verified it in January. -> VERIFIED

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