Comment 61 for bug 330460

Woohoo!

commit e2bf07fe23fd11a2acba609bf34ccc59c5553389
Author: Chris Wilson <email address hidden>
Date: Sat Aug 7 11:01:24 2010 +0100

    drm/i915: Implement fair lru eviction across both rings. (v2)

    Based in a large part upon Daniel Vetter's implementation and adapted
    for handling multiple rings in a single pass.

    This should lead to better gtt usage and fixes the page-fault-of-doom
    triggered. The fairness is provided by scanning through the GTT space
    amalgamating space in rendering order. As soon as we have a contiguous
    space in the GTT large enough for the new object (and its alignment),
    evict any object which lies within that space. This should keep more
    objects resident in the GTT.

    Doing throughput testing on a PineView machine with cairo-perf-trace
    indicates that there is very little difference with the new LRU scan,
    perhaps a small improvement... Except oddly for the poppler trace.

    Reference:

      Bug 15911 - Intermittent X crash (freeze)
      https://bugzilla.kernel.org/show_bug.cgi?id=15911

      Bug 20152 - cannot view JPG in firefox when running UXA
      https://bugs.freedesktop.org/show_bug.cgi?id=20152

      Bug 24369 - Hang when scrolling firefox page with window in front
      https://bugs.freedesktop.org/show_bug.cgi?id=24369

      Bug 28478 - Intermittent graphics lockups due to overflow/loop
      https://bugs.freedesktop.org/show_bug.cgi?id=28478

    v2: Attempt to clarify the logic and order of eviction through the use
    of comments and macros.

    Signed-off-by: Chris Wilson <email address hidden>
    Reviewed-by: Daniel Vetter <email address hidden>
    Signed-off-by: Eric Anholt <email address hidden>