<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - [SKL dmc] Headless mode media transcoding is 20-30% slower comparing to connected monitor use case" href="https://bugs.freedesktop.org/show_bug.cgi?id=100572#c8">Comment # 8</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - [SKL dmc] Headless mode media transcoding is 20-30% slower comparing to connected monitor use case" href="https://bugs.freedesktop.org/show_bug.cgi?id=100572">bug 100572</a> from <a class="email" href="mailto:imre.deak@intel.com" title="Imre Deak <imre.deak@intel.com>"> Imre Deak</a> <pre>(In reply to Imre Deak from <a href="show_bug.cgi?id=100572#c7">comment #7</a>) > (In reply to Tvrtko Ursulin from <a href="show_bug.cgi?id=100572#c6">comment #6</a>) > > I tried not loading the DMC firmware and can confirm that the issue is not > > present in that case. > > > > Also, it is possible to reproduce this in the default kernel config (no > > pinning is required) simply with igt/benchmarks/gem_latency -n 0 in which > > case the perf difference between the two setups was ~8x in my testing. > > One possibility is that DC6 enables deeper system level power states and > this causes latency elsewhere. What are the PC state residencies shown by > powertop or the kernel's tools/power/x86/turbostat when DMC is loaded and > not? > > What's the effect of limiting max_cstates to 0 (and having DMC loaded)? > > An other problem could be that the GPU is trying to access the display, > (maybe checking scan line counts or something?). > > Does /sys/kernel/debug/dri/0/i915_dmc_info show any transitions during the > test when DMC is loaded? Also the actual RC6 residency reported by powertop/turbostat would be interesting. (even though it's disabled)</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>