Re: 13.0-RC2 / 14-CURRENT: Processes getting stuck in vlruwk state

From: Mateusz Guzik <mjguzik_at_gmail.com>
Date: Wed, 17 Mar 2021 18:55:43 +0100
Thanks, I'm going to have to ponder a little bit.

In the meantime can you apply this:
https://people.freebsd.org/~mjg/maxvnodes.diff

Once you boot, tweak maxvnodes:
sysctl kern.maxvnodes=1049226

Run poudriere. Once it finishes, inspect sysctl vfs.highest_numvnodes

On 3/17/21, Yamagi <lists_at_yamagi.org> wrote:
> Hi Mateusz,
> the sysctl output after about 10 minutes into the problem is attached.
> In case that its stripped by Mailman a copy can be found here:
> https://deponie.yamagi.org/temp/sysctl_vlruwk.txt.xz
>
> Regards,
> Yamagi
>
> On Wed, 17 Mar 2021 15:57:59 +0100
> Mateusz Guzik <mjguzik_at_gmail.com> wrote:
>
>> Can you reproduce the problem and run obtain "sysctl -a"?
>>
>> In general, there is a vnode limit which is probably too small. The
>> reclamation mechanism is deficient in that it will eventually inject
>> an arbitrary pause.
>>
>> On 3/17/21, Yamagi <lists_at_yamagi.org> wrote:
>> > Hi,
>> > me and some other users in the ##bsdforen.de IRC channel have the
>> > problem that during Poudriere runs processes getting stuck in the
>> > 'vlruwk' state.
>> >
>> > For me it's fairly reproduceable. The problems begin about 20 to 25
>> > minutes after I've started poudriere. At first only some ccache
>> > processes hang in the 'vlruwk' state, after another 2 to 3 minutes
>> > nearly everything hangs and the total CPU load drops to about 5%.
>> > When I stop poudriere with ctrl-c it takes another 3 to 5 minutes
>> > until the system recovers.
>> >
>> > First the setup:
>> > * poudriere runs in a bhyve vm on zvol. The host is a 12.2-RELEASE-p2.
>> >   The zvol has a 8k blocksize, the guests partition are aligned to 8k.
>> >   The guest has only zpool, the pool was created with ashift=13. The
>> >   vm has 16 E5-2620 and 16 gigabytes RAM assigned to it.
>> > * poudriere is configured with ccache and ALLOW_MAKE_JOBS=yes. Removing
>> >   either of these options lowers the probability of the problem to show
>> >   up significantly.
>> >
>> > I've tried several git revisions starting with 14-CURRENT at
>> > 54ac6f721efccdba5a09aa9f38be0a1c4ef6cf14 in the hope that I can find at
>> > least one known to be good revision. No chance, even a kernel build
>> > from 0932ee9fa0d82b2998993b649f9fa4cc95ba77d6 (Wed Sep 2 19:18:27 2020
>> > +0000) has the problem. The problem isn't reproduceable with
>> > 12.2-RELEASE.
>> >
>> > The kernel stack ('procstat -kk') of a hanging process is:
>> > mi_switch+0x155 sleepq_switch+0x109 sleepq_catch_signals+0x3f1
>> > sleepq_wait_sig+0x9 _sleep+0x2aa kern_wait6+0x482 sys_wait4+0x7d
>> > amd64_syscall+0x140 fast_syscall_common+0xf8
>> >
>> > The kernel stack of vnlru is changing, even while the processes are
>> > hanging:
>> > * mi_switch+0x155 sleepq_switch+0x109 sleepq_timedwait+0x4b
>> > _sleep+0x29b vnlru_proc+0xa05 fork_exit+0x80 fork_trampoline+0xe
>> > * fork_exit+0x80 fork_trampoline+0xe
>> >
>> > Since vnlru is accumulating CPU time it looks like it's doing at least
>> > something. As an educated guess I would say that vn_alloc_hard() is
>> > waiting a long time or even forever to allocate new vnodes.
>> >
>> > I can provide more information, I just need to know what.
>> >
>> >
>> > Regards,
>> > Yamagi
>> >
>> > --
>> > Homepage: https://www.yamagi.org
>> > Github:   https://github.com/yamagi
>> > GPG:      0x1D502515
>> >
>>
>>
>> --
>> Mateusz Guzik <mjguzik gmail.com>
>
>
> --
> Homepage: https://www.yamagi.org
> Github:   https://github.com/yamagi
> GPG:      0x1D502515
>


-- 
Mateusz Guzik <mjguzik gmail.com>
Received on Wed Mar 17 2021 - 16:55:46 UTC

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