Date: Thu, 2 Jul 2020 10:40:50 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: Gordon Bergling <gbe@freebsd.org>, Allan Jude <allanjude@freebsd.org> Cc: freebsd-hackers@freebsd.org Subject: Re: Constant load of 1 on a recent 12-STABLE Message-ID: <0a10a722-3eec-456b-d771-97a49af89ad1@FreeBSD.org> In-Reply-To: <20200623072332.GA54653@lion.0xfce3.net> References: <20200603101607.GA80381@lion.0xfce3.net> <c18664e8-b4e3-1402-48ed-3a02dc36ce29@freebsd.org> <20200603202929.GA65032@lion.0xfce3.net> <8b1498ea-e343-506e-79c7-c25b594808f0@freebsd.org> <20200604123720.GA63595@lion.0xfce3.net> <20200623072332.GA54653@lion.0xfce3.net>
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On 23/06/2020 10:23, Gordon Bergling wrote:
> What is maybe also related to the problem is the following top output,
> collected by 'top -HS'. The three zfskern threads generate little load, but that
> constant. The annoying part of the problem is, that the load of 1 is reported and
> that the hostsystem schedules the thread over all 4 physical cores and keeps the
> clockrate at the highest frequency.
>
> PID USERNAME PRI NICE SIZE RES STATE C TIME WCPU COMMAND
> 11 root 155 ki31 0B 64K CPU2 2 17:28 97.39% idle{idle: cpu2}
> 11 root 155 ki31 0B 64K CPU3 3 17:29 96.78% idle{idle: cpu3}
> 11 root 155 ki31 0B 64K CPU1 1 17:29 96.40% idle{idle: cpu1}
> 11 root 155 ki31 0B 64K RUN 0 17:25 96.13% idle{idle: cpu0}
> 8 root -8 - 0B 1040K mmp->m 2 0:44 4.32% zfskern{mmp_thread_enter}
> 8 root -8 - 0B 1040K mmp->m 1 0:44 4.28% zfskern{mmp_thread_enter}
> 8 root -8 - 0B 1040K mmp->m 3 0:44 4.25% zfskern{mmp_thread_enter}
>
> Does anyone has some insight where zfskern is spawned? I maybe can bisect then the resulting change
> which leads to this behaviour.
That's strange. Those mmp threads shouldn't really be consuming much CPU.
Normally they should just sleep all the time.
Do you use the new ZFS multi-modifier protection feature? I guess not.
Do you have 'multihost' property set on any of your pools?
The change you were looking for is
r361383 MFC r354804,r354806,r354807,r354885: 10499 Multi-modifier protection (MMP)
--
Andriy Gapon
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