Date: Thu, 29 Oct 2015 22:59:00 +0100 From: Miroslav Lachman <000.fbsd@quip.cz> To: Jeremy Chadwick <jdc@koitsu.org> Cc: freebsd-stable@freebsd.org Subject: Re: stable/10: high load average when box is idle Message-ID: <563296A4.70501@quip.cz> In-Reply-To: <56320737.2060901@quip.cz> References: <20151027050508.GA7612@icarus.home.lan> <5631EE40.3020404@quip.cz> <20151029100910.GA52255@icarus.home.lan> <56320737.2060901@quip.cz>
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Miroslav Lachman wrote on 10/29/2015 12:47: > Jeremy Chadwick wrote on 10/29/2015 11:09: [...] >> I've seen it on both bare-metal and VMs. Please see c#8 in the ticket; >> there's an itemised list of where I've seen it, but I'm sure it's not >> limited to just those. > > OK, I have read your c#8 and did some tests on our affected VMs. > With sysctl kern.eventtimer.periodic=1 it is better. Where previously > load were about 0.40 is 0.15 now. > One of these three systems is FreeBSD 10.2 and on this machine the > positive effect of kern.eventtimer.periodic=1 is more visible - load is > now 0.00 - 0.05. > I don't know if this is some coincidence or something is different in 10.2. > > Settings of kern.eventtimer is the same on all VMs > > kern.eventtimer.et.LAPIC.flags: 7 > kern.eventtimer.et.LAPIC.frequency: 35071418 > kern.eventtimer.et.LAPIC.quality: 600 > kern.eventtimer.et.i8254.flags: 1 > kern.eventtimer.et.i8254.frequency: 1193182 > kern.eventtimer.et.i8254.quality: 100 > kern.eventtimer.et.RTC.flags: 17 > kern.eventtimer.et.RTC.frequency: 32768 > kern.eventtimer.et.RTC.quality: 0 > kern.eventtimer.choice: LAPIC(600) i8254(100) RTC(0) > kern.eventtimer.singlemul: 4 > kern.eventtimer.idletick: 0 > kern.eventtimer.timer: LAPIC > kern.eventtimer.periodic: 1 Just for the record - I added graphs of CPU load from these three VMs FreeBSD 10.1 http://imagebin.ca/v/2Kkyq29M13d3 FreeBSD 10.1 http://imagebin.ca/v/2KkzUccxJEoE FreeBSD 10.2 http://imagebin.ca/v/2Kl00mS4RQ3n And coresponding CPU idle percentages FreeBSD 10.1 http://imagebin.ca/v/2Kl0R0U1pRhg FreeBSD 10.1 http://imagebin.ca/v/2Kl0cYiB0mS4 FreeBSD 10.2 http://imagebin.ca/v/2Kl0lIipTKXc As I mentioned the difference with / without kern.eventtimer.periodic=1 is more visible on FreeBSD 10.2. The flat line on the graphs is interval where I disabled almost all services - crontab too - so no measurements in this time. Effect of kern.eventtimer.periodic=1 is visible from 18:00 when I started all usual services. Miroslav Lachman
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