On 03/13/2018 12:33 PM, Schrenkhammer, Martin wrote: > I am currently porting a project from Haswell to Skylake (i5-6440EQ). When in > desktop, I observe latency peaks when windows are moved around or zoomed. > With Haswell CPUs, there is not impact of graphic workload. Unfortunately > everything above 10us is an issue in our real time system application. > Currently I am using Xubuntu 16.04 + Kernel 4.9.51 + Xenomai 3.0.6 > I already disabled all power- and performance features like Hyper-Threading, > SpeedStep, Turbo Mode, C-States in BIOS and also by kernel parameters. Also > disabled i915 power savings like i915.enable_dc=0, i915.enable_rc6=0, > i915.enable_execlists=0... and disabled grafik turbo gt_max_freq_mhz = 350 > gt_boost_freq_mhz = 350 > > One difference we see between Haswell and Skylake: i915 raises a lot of MSI > when moving windows around where there are almost zero at Haswell. > > Any ideas for bringing the peaks down?
Did you track which specific event the i915 driver was handling with those MSIs? > > == Sampling period: 100 us > == Test mode: periodic user-mode task > == All results in microseconds > warming up... > RTT| 00:00:01 (periodic user-mode task, 100 us period, priority 99) > RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat best|--lat > worst > RTD| -0.368| -0.210| 0.259| 0| 0| -0.368| > 0.259 > RTD| -0.259| -0.161| 1.601| 0| 0| -0.368| > 1.601 > RTD| -0.290| -0.174| 1.367| 0| 0| -0.368| > 1.601 This is unrelated to the issue at stake, but the core timer looks slightly early (negative mins), which means that the expected intrinsic latency value is too pessimistic/high. Running autotune may help in picking better gravity values for this timer. -- Philippe. _______________________________________________ Xenomai mailing list Xenomai@xenomai.org https://xenomai.org/mailman/listinfo/xenomai
