[Bug 90671] New: [HSW bisected] SynMark2_v6_0_0_OglBatch1 performance reduce by 14% with gnome-session

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=90671

            Bug ID: 90671
           Summary: [HSW bisected] SynMark2_v6_0_0_OglBatch1 performance
                    reduce by 14% with gnome-session
           Product: DRI
           Version: unspecified
          Hardware: All
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: yex.tian at intel.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

System Environment:       
Platform:  HSW
Kernel:  (drm-intel-nightly)7e83d3b288f06c29d5ab4f870b84db5fccfa3a08
Libdrm: (master)libdrm-2.4.61-2-ga1acffd4e0968ffa65b673163574188a00c9ab7e
Mesa: (master)3ec18152858fd9aadb398d78d5ad2d2b938507c1
Xserver:   
(master)xorg-server-1.17.0-151-gad02d0df75318660c3f7cd6063eac409327fe560
Xf86_video_intel:   
(master)2.99.917-312-ga6dd2655cb41000943e554ccea16e5781bcbf012
Cairo: (master)2cf2d8e340a325adb205baf8e4bd64e1d1858008
Libva:  (master)4763db1c2133d4e6b92355938ecb6f23a7767b6b
Libva_intel_driver: (master)4a1c4d21f3428b08ef765d7f7de75b97006514ac

Bug detailed description:
--------------------------------------------------
SynMark2_v6_0_0_OglBatch1 performance reduce by 12% with gnome-session on HSW.
It’s kernel regression. By bisected, show that b471618 is the first bad commit.
This bug will affect the following cases:
OglBatch1-- OglBatch5 reduced by 14%
OglGeomTriStrip reduced by 12%
OglPSBump2 reduced by 9%
OglVSDiffuse1 reduced by 9%
OglVSDiffuse8 reduced by 9%
OglVSTangent reduced by 9%

commit b47161858ba13c9c7e03333132230d66e008dd55
Author:     Chris Wilson <chris at chris-wilson.co.uk>
AuthorDate: Mon Apr 27 13:41:17 2015 +0100
Commit:     Daniel Vetter <daniel.vetter at ffwll.ch>
CommitDate: Thu May 21 15:11:42 2015 +0200

    drm/i915: Implement inter-engine read-read optimisations

    Currently, we only track the last request globally across all engines.
    This prevents us from issuing concurrent read requests on e.g. the RCS
    and BCS engines (or more likely the render and media engines). Without
    semaphores, we incur costly stalls as we synchronise between rings -
    greatly impacting the current performance of Broadwell versus Haswell in
    certain workloads (like video decode). With the introduction of
    reference counted requests, it is much easier to track the last request
    per ring, as well as the last global write request so that we can
    optimise inter-engine read read requests (as well as better optimise
    certain CPU waits).

Please see Xrog and dmesg info.

Reproduce steps:
----------------------------
1, xinit& 
2, gnome-session&
3, ./synmark2 OglBatch1

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