[Bug 107600] Regression: stuttering H.264 video w/ mythtv on old laptop w/ 915GM igp

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=107600

--- Comment #31 from Chris Wilson <chris at chris-wilson.co.uk> ---
Though it doesn't explain what's going wrong, it does paper over the problem
with better utilization of memory:

commit c8124d399224d626728e2ffb95a1d564a7c06968
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Thu Sep 6 20:01:43 2018 +0100

    drm/i915/overlay: Allocate physical registers from stolen

    Given that we are now reasonably confident in our ability to detect and
    reserve the stolen memory (physical memory reserved for graphics by the
    BIOS) for ourselves on most machines, we can put it to use. In this
    case, we need a page to hold the overlay registers.

    On an i915g running MythTv, H Buus noticed that

            commit 6a2c4232ece145d8b5a8f95f767bd6d0d2d2f2bb
            Author: Chris Wilson <chris at chris-wilson.co.uk>
            Date:   Tue Nov 4 04:51:40 2014 -0800
            drm/i915: Make the physical object coherent with GTT

    introduced stuttering into his video playback. After discarding the
    likely suspect of it being the physical cursor updates, we were left
    with the use of the phys object for the overlay. And lo, if we
    completely avoid using the phys object (allocated just once on module
    load!) by switching to stolen memory, the stuttering goes away.

    For lack of a better explanation, claim victory and kill two birds with
    one stone.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107600
    Fixes: 6a2c4232ece1 ("drm/i915: Make the physical object coherent with
GTT")
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
    Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
    Link:
https://patchwork.freedesktop.org/patch/msgid/20180906190144.1272-1-chris@chris-wilson.co.uk


We should keep this bug open for a little while longer to see if we can narrow
down where phys is playing up.

-- 
You are receiving this mail because:
You are the assignee for the bug.
You are on the CC list for the bug.
You are the QA Contact for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/intel-gfx-bugs/attachments/20180911/be9eb905/attachment.html>