Jeremy Chadwick wrote on 10/29/2015 11:09:> On Thu, Oct 29, 2015 at 11:00:32AM +0100, Miroslav Lachman wrote:
>> Jeremy Chadwick wrote on 10/27/2015 06:05:
>>> (I am not subscribed to the mailing list, please keep me CC'd)
>>>
>>> Issue: a stable/10 system that has an abnormally high load average
(e.g.
>>> 0.15, but may be higher depending on other variables which I
can't
>>> account for) when the machine is definitely idle (i.e. cannot be
traced
>>> to high interrupt usage per vmstat -i, cannot be traced to a
userland
>>> process or kernel thread, etc.).
>>>
>>> This problem has been discussed many times on the FreeBSD mailing
lists
>>> and the FreeBSD forum (including some folks seeing it on 9.x, but
my
>>> complaint here is focused on 10.x so please focus there).
>>>
>>> I'd politely like to request that anyone experiencing this, or
who has
>>> experienced it (and if you know when it stopped or why, including
what
>>> you may have done, include that), to chime in on this ticket from
2012
>>> (made for 9.x but style of issue still applies; c#5 is quite
valid):
>>>
>>> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=173541
>>>
>>> For those still experiencing it, I'd suggest reading c#8 and
seeing if
>>> sysctl kern.eventtimer.periodic=1 relieves the problem for you.
(At
>>> this time I would not suggest leaving that set indefinitely, as it
does
>>> seem to increase the interrupt rate in cpuX:timer in vmstat -i.
But for
>>> me kern.eventtimer.periodic=1 "fixes" the issue)
>>
>> Is it on real HW server or in some kind of virtualization? I am seeing
load
>> 0.5 - 1.2 on three virtual machines in VMware. The machines are without
any
>> traffic. Just fresh instalation of FreeBSD 10.1 and some services
without
>> any public content.
>
> 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
Miroslav Lachman