<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_REOPENED " title="REOPENED - [BDW Bisected] OglDrvCtx performance reduced by ~30% after use true PPGTT in Gen8+" href="https://bugs.freedesktop.org/show_bug.cgi?id=87726#c8">Comment # 8</a> on <a class="bz_bug_link bz_status_REOPENED " title="REOPENED - [BDW Bisected] OglDrvCtx performance reduced by ~30% after use true PPGTT in Gen8+" href="https://bugs.freedesktop.org/show_bug.cgi?id=87726">bug 87726</a> from <a class="email" href="mailto:chris@chris-wilson.co.uk" title="Chris Wilson <chris@chris-wilson.co.uk>"> Chris Wilson</a> <pre>One step forward, several back in the meantime: commit db6c2b4151f2915fe1695cdcac43b32e73d1ad32 Author: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>> Date: Tue Nov 1 11:54:00 2016 +0000 drm/i915: Store the vma in an rbtree under the object With full-ppgtt one of the main bottlenecks is the lookup of the VMA underneath the object. For execbuf there is merit in having a very fast direct lookup of ctx:handle to the vma using a hashtree, but that still leaves a large number of other lookups. One way to speed up the lookup would be to use a rhashtable, but that requires extra allocations and may exhibit poor worse case behaviour. An alternative is to use an embedded rbtree, i.e. no extra allocations and deterministic behaviour, but at the slight cost of O(lgN) lookups (instead of O(1) for rhashtable). The major of such tree will be very shallow and so not much slower, and still scales much, much better than the current unsorted list.</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> <li>You are the assignee for the bug.</li> <li>You are on the CC list for the bug.</li> </ul> </body> </html>