Quoting Francisco Jerez (2018-07-28 06:20:12) > Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes: > > > A recent trend for cpufreq is to boost the CPU frequencies for > > iowaiters, in particularly to benefit high frequency I/O. We do the same > > and boost the GPU clocks to try and minimise time spent waiting for the > > GPU. However, as the igfx and CPU share the same TDP, boosting the CPU > > frequency will result in the GPU being throttled and its frequency being > > reduced. Thus declaring iowait negatively impacts on GPU throughput. > > > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107410 > > References: 52ccc4314293 ("cpufreq: intel_pstate: HWP boost performance on IO wakeup") > > This patch causes up to ~13% performance regressions (with significance > 5%) on several latency-sensitive tests on my BXT: > > jxrendermark/rendering-test=Linear Gradient Blend/rendering-size=128x128: XXX ±35.69% x53 -> XXX ±32.57% x61 d=-13.52% ±31.88% p=2.58% Curious, as this is just a bunch of composites and as with the others, should never be latency sensitive (at least under bare X11). Fwiw, I double checked this result: Broxton J3455, jxrend -num $(for i in $(seq 1 100); do echo 12 128; done) x noio-1.txt + io-1.txt +------------------------------------------------------------------------+ | + | | + | | * | | +*x | | + +***+ | | + +***++ | | + ****+* + | | ++x****** x+ x | | xx **x*******+x* xx* | | + + xx*xx+***********x**x***x x+ | |x x+** x**x****************x***x***+ x + x x ++ +| | |_______MA_______| | | |________MA__________| | +------------------------------------------------------------------------+ N Min Max Median Avg Stddev x 100 16109.095 16211.579 16152.497 16154.87 19.270749 + 100 16116.47 16274.973 16152.365 16156.954 25.304398 No difference proven at 95.0% confidence Your variance is much, much higher, are you still using the original jxrendermark that doesn't wait for rendering completion? -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
