[Bug 87725] [BDW] OglBatch7 performance reduced by ~7% after enable execlists

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=87725

Chris Wilson <chris at chris-wilson.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |WONTFIX
             Status|NEEDINFO                    |RESOLVED

--- Comment #21 from Chris Wilson <chris at chris-wilson.co.uk> ---
Minor improvements, but still the disparity remains. However,

commit 79e6770cb1f5e32eb49590edbb794a97d0113aed
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Mon Nov 20 20:55:01 2017 +0000

    drm/i915: Remove obsolete ringbuffer emission for gen8+

    Since removing the module parameter to force selection of ringbuffer
    emission for gen8, the code is defunct. Remove it.

    To put the difference into perspective, a couple of microbenchmarks
    (bdw i7-5557u, 20170324):
                                            ring          execlists
    exec continuous nops on all rings:   1.491us            2.223us
    exec sequential nops on each ring:  12.508us           53.682us
    single nop + sync:                   9.272us           30.291us

    vblank_mode=0 glxgears:            ~11000fps           ~9000fps

    Since the earlier submission, gen8 ringbuffer submission has fallen
    further and further behind in features. So while ringbuffer may hold the
    throughput crown, in terms of interactive latency, execlists is much
    better. Alas, we have no convenient metrics for such, other than
    demonstrating things we can do with execlists but can not using
    legacy ringbuffer submission.

    We have made a few improvements to lowlevel execlists throughput,
    and ringbuffer currently panics on boot! (bdw i7-5557u, 20171026):

                                            ring          execlists
    exec continuous nops on all rings:       n/a            1.921us
    exec sequential nops on each ring:       n/a           44.621us
    single nop + sync:                       n/a           21.953us

    vblank_mode=0 glxgears:                  n/a          ~18500fps

    References: https://bugs.freedesktop.org/show_bug.cgi?id=87725
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Once-upon-a-time-Reviewed-by: Joonas Lahtinen
<joonas.lahtinen at linux.intel.com>
    Reviewed-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
    Link:
https://patchwork.freedesktop.org/patch/msgid/20171120205504.21892-2-chris@chris-wilson.co.uk

commit fb5c551ad510e4a408c105670f89c725ebbfe6c8
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Mon Nov 20 20:55:00 2017 +0000

    drm/i915: Remove i915.enable_execlists module parameter

    Execlists and legacy ringbuffer submission are no longer feature
    comparable (execlists now offer greater functionality that should
    overcome their performance hit) and obsoletes the unsafe module
    parameter, i.e. comparing the two modes of execution is no longer
    useful, so remove the debug tool.

    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
    Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
    Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com> #i915_perf.c
    Link:
https://patchwork.freedesktop.org/patch/msgid/20171120205504.21892-1-chris@chris-wilson.co.uk

-- 
You are receiving this mail because:
You are the assignee for the bug.
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/intel-gfx-bugs/attachments/20171123/5e9f291b/attachment.html>