Re: vnode_init took over 6 minutes

> On Oct 31, 2023, at 10:16, Mateusz Guzik <mjguzik@gmail.com> wrote:
> 
> On 10/31/23, John F Carr <jfc@mit.edu> wrote:
>> During a poudriere build control-T showed an awk process was stuck
>> for over 6 minutes trying to acquire a lock in vnode_init.
>> 
>> load: 8.58  cmd: awk 51238 [running] 392.88r 0.00u 392.88s 100% 2604k
>> __mtx_lock_sleep+0xf8 __mtx_lock_flags+0xa4 vnode_init+0xc3
>> keg_alloc_slab+0x277 zone_import+0x143 cache_alloc+0x3ed
>> cache_alloc_retry+0x23 getnewvnode_reserve+0x20 zfs_zget+0x1f
>> zfs_dirent_lookup+0x16d zfs_dirlook+0x7f zfs_lookup+0x3e0
>> zfs_freebsd_cachedlookup+0x74 vfs_cache_lookup+0xa7
>> cache_fplookup_noentry+0x241 cache_fplookup+0x575 namei+0x1ea
>> vn_open_cred+0x48d
>> 
>> The stack trace was the same for several minutes.  System CPU time was
>> increasing.
>> 
>> Address vnode_init+0xc3 corresponds to the mtx_lock call here.
>> 
>> vp->v_holdcnt = VHOLD_NO_SMR;
>> vp->v_type = VNON;
>> mtx_lock(&vnode_list_mtx);
>> TAILQ_INSERT_BEFORE(vnode_list_free_marker, vp, v_vnodelist);
>> mtx_unlock(&vnode_list_mtx);
>> return (0);
>> 
>> Address __mtx_lock_sleep+0xf8 is the instruction after a call to
>> lock_delay.
>> 
>> ps says the command line was
>> 
>> /usr/bin/awk -f /usr/bin/awk
>> old-default/2023-10-31_08h21m03s/.poudriere.builders
>> old-default/2023-10-31_08h21m03s/.poudriere.buildname ...
>> 
>> with the full list of input files exceeding the ~2KB command line length
>> limit of ps.
>> "/usr/bin/awk" is probably not the real second argument.  It would cause an
>> immediate syntax error.
>> 
>> The hang resolved within a few more minutes and poudriere is continuing
>> happily.
>> 
>> I have never seen such behavior before.  Code in vfs_subr.c tries not to
>> hold the
>> vnode_list_mtx lock for too long.
>> 
>> Any thoughts?
>> 
>> 
>> FreeBSD 13.2-STABLE up through commit b180f0040f95, 24 core 48 thread Zen
>> 2,
>> zfs pool on SSD connected via 12 Gbps SAS with cache on NVME, 160 GB RAM.
>> 
> 
> what does "sysctl vfs.vnode" say
> 
> 
> -- 
> Mateusz Guzik <mjguzik gmail.com>

With the builds now complete,

vfs.vnode.vnlru.uma_reclaim_calls: 0
vfs.vnode.vnlru.kicks: 0
vfs.vnode.vnlru.max_free_per_call: 10000
vfs.vnode.vnlru.failed_runs: 0
vfs.vnode.vnlru.direct_recycles_free: 152871194
vfs.vnode.vnlru.recycles_free: 77190881
vfs.vnode.vnlru.recycles: 0
vfs.vnode.stats.alloc_sleeps: 0
vfs.vnode.stats.free: 1269702
vfs.vnode.stats.skipped_requeues: 9375158
vfs.vnode.stats.created: 235594976
vfs.vnode.stats.count: 1407640
vfs.vnode.param.wantfree: 681059
vfs.vnode.param.limit: 2724237

Uptime is 11 days, mostly with low I/O rates.