Re: nullfs and ZFS issues
- Reply: Doug Ambrisko : "Re: nullfs and ZFS issues"
- Reply: Alexander Leidinger : "Re: nullfs and ZFS issues"
- In reply to: Doug Ambrisko : "Re: nullfs and ZFS issues"
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Date: Fri, 22 Apr 2022 07:04:39 UTC
Quoting Doug Ambrisko <ambrisko@ambrisko.com> (from Thu, 21 Apr 2022 09:38:35 -0700): > On Thu, Apr 21, 2022 at 03:44:02PM +0200, Alexander Leidinger wrote: > | Quoting Mateusz Guzik <mjguzik@gmail.com> (from Thu, 21 Apr 2022 > | 14:50:42 +0200): > | > | > On 4/21/22, Alexander Leidinger <Alexander@leidinger.net> wrote: > | >> I tried nocache on a system with a lot of jails which use nullfs, > | >> which showed very slow behavior in the daily periodic runs (12h runs > | >> in the night after boot, 24h or more in subsequent nights). Now the > | >> first nightly run after boot was finished after 4h. > | >> > | >> What is the benefit of not disabling the cache in nullfs? I would > | >> expect zfs (or ufs) to cache the (meta)data anyway. > | >> > | > > | > does the poor performance show up with > | > https://people.freebsd.org/~mjg/vnlru_free_pick.diff ? > | > | I would like to have all the 22 jails run the periodic scripts a > | second night in a row before trying this. > | > | > if the long runs are still there, can you get some profiling from it? > | > sysctl -a before and after would be a start. > | > > | > My guess is that you are the vnode limit and bumping into the 1 > second sleep. > | > | That would explain the behavior I see since I added the last jail > | which seems to have crossed a threshold which triggers the slow > | behavior. > | > | Current status (with the 112 nullfs mounts with nocache): > | kern.maxvnodes: 10485760 > | kern.numvnodes: 3791064 > | kern.freevnodes: 3613694 > | kern.cache.stats.heldvnodes: 151707 > | kern.vnodes_created: 260288639 > | > | The maxvnodes value is already increased by 10 times compared to the > | default value on this system. > > I've attached mount.patch that when doing mount -v should > show the vnode usage per filesystem. Note that the problem I was > running into was after some operations arc_prune and arc_evict would > consume 100% of 2 cores and make ZFS really slow. If you are not > running into that issue then nocache etc. shouldn't be needed. I don't run into this issue, but I have a huge perf difference when using nocache in the nightly periodic runs. 4h instead of 12-24h (22 jails on this system). > On my laptop I set ARC to 1G since I don't use swap and in the past > ARC would consume to much memory and things would die. When the > nullfs holds a bunch of vnodes then ZFS couldn't release them. > > FYI, on my laptop with nocache and limited vnodes I haven't run > into this problem. I haven't tried the patch to let ZFS free > it's and nullfs vnodes on my laptop. I have only tried it via I have this patch and your mount patch installed now, without nocache and reduced arc reclaim settings (100, 1). I will check the runtime for the next 2 days. Your mount patch to show the per mount vnodes count looks useful, not only for this particular case. Do you intend to commit it? Bye, Alexander. -- http://www.Leidinger.net Alexander@Leidinger.net: PGP 0x8F31830F9F2772BF http://www.FreeBSD.org netchild@FreeBSD.org : PGP 0x8F31830F9F2772BF