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

To sum up what happened, Yamagi was kind enough to test several
patches and ultimately the issue got solved here
https://cgit.freebsd.org/src/commit/?id=e9272225e6bed840b00eef1c817b188c172338ee
. The patch also got merged into releng/13.0

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>