4.16 required? https://www.phoronix.com/scan.php?page=news_item&px=Skylake-X-P-State-Linux- 4.16 -----Original Message----- From: ceph-users <ceph-users-bounces@xxxxxxxxxxxxxx> On Behalf Of Blair Bethwaite Sent: 01 May 2018 16:46 To: Wido den Hollander <wido@xxxxxxxx> Cc: ceph-users <ceph-users@xxxxxxxxxxxxxx>; Nick Fisk <nick@xxxxxxxxxx> Subject: Re: Intel Xeon Scalable and CPU frequency scaling on NVMe/SSD Ceph OSDs Also curious about this over here. We've got a rack's worth of R740XDs with Xeon 4114's running RHEL 7.4 and intel-pstate isn't even active on them, though I don't believe they are any different at the OS level to our Broadwell nodes (where it is loaded). Have you tried poking the kernel's pmqos interface for your use-case? On 2 May 2018 at 01:07, Wido den Hollander <wido@xxxxxxxx> wrote: > Hi, > > I've been trying to get the lowest latency possible out of the new > Xeon Scalable CPUs and so far I got down to 1.3ms with the help of Nick. > > However, I can't seem to pin the CPUs to always run at their maximum > frequency. > > If I disable power saving in the BIOS they stay at 2.1Ghz (Silver > 4110), but that disables the boost. > > With the Power Saving enabled in the BIOS and when giving the OS all > control for some reason the CPUs keep scaling down. > > $ echo 100 > /sys/devices/system/cpu/intel_pstate/min_perf_pct > > cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009 Report > errors and bugs to cpufreq@xxxxxxxxxxxxxxx, please. > analyzing CPU 0: > driver: intel_pstate > CPUs which run at the same hardware frequency: 0 > CPUs which need to have their frequency coordinated by software: 0 > maximum transition latency: 0.97 ms. > hardware limits: 800 MHz - 3.00 GHz > available cpufreq governors: performance, powersave > current policy: frequency should be within 800 MHz and 3.00 GHz. > The governor "performance" may decide which speed to use > within this range. > current CPU frequency is 800 MHz. > > I do see the CPUs scale up to 2.1Ghz, but they quickly scale down > again to 800Mhz and that hurts latency. (50% difference!) > > With the CPUs scaling down to 800Mhz my latency jumps from 1.3ms to > 2.4ms on avg. With turbo enabled I hope to get down to 1.1~1.2ms on avg. > > $ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor > performance > > Everything seems to be OK and I would expect the CPUs to stay at > 2.10Ghz, but they aren't. > > C-States are also pinned to 0 as a boot parameter for the kernel: > > processor.max_cstate=1 intel_idle.max_cstate=0 > > Running Ubuntu 16.04.4 with the 4.13 kernel from the HWE from Ubuntu. > > Has anybody tried this yet with the recent Intel Xeon Scalable CPUs? > > Thanks, > > Wido > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com -- Cheers, ~Blairo _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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