<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - 2x Media CPU power usage, or 15% perf drop when CPU bound GPU use-case is TDP limited" href="https://bugs.freedesktop.org/show_bug.cgi?id=108700#c7">Comment # 7</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - 2x Media CPU power usage, or 15% perf drop when CPU bound GPU use-case is TDP limited" href="https://bugs.freedesktop.org/show_bug.cgi?id=108700">bug 108700</a> from <a class="email" href="mailto:eero.t.tamminen@intel.com" title="Eero Tamminen <eero.t.tamminen@intel.com>"> Eero Tamminen</a> <pre>We don't specifically enable any mitigations, just use drm-tip kernel defaults. It seems to have enabled an additional one when it was rebased to 4.20-rc1: Spectre V2 : Spectre v2 cross-process SMT mitigation: Enabling STIBP Threading in the listed test-cases: * MediaSDK 50 stream transcode case has 250 threads * I thought GfxBench Driver2 doesn't thread, as only single CPU is busy, but it actually uses 3 threads of which 2 use as much CPU as they can, and apparently kernel just sticks them to same core, so they seem hyperthreaded -> I think that SMT mitigation is very likely cause for the drop instead of i915. Could you point out suitable drm-tip commit IDs before and after enabling the mitigation so that I could verify it?</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are on the CC list for the bug.</li> <li>You are the assignee for the bug.</li> <li>You are the QA Contact for the bug.</li> </ul> </body> </html>