On 4/21/22, Alexander Leidinger <alexan...@leidinger.net> wrote: > Quoting Doug Ambrisko <ambri...@ambrisko.com> (from Wed, 20 Apr 2022 > 09:20:33 -0700): > >> On Wed, Apr 20, 2022 at 11:39:44AM +0200, Alexander Leidinger wrote: >> | Quoting Doug Ambrisko <ambri...@ambrisko.com> (from Mon, 18 Apr 2022 >> | 16:32:38 -0700): >> | >> | > With nullfs, nocache and settings max vnodes to a low number I can >> | >> | Where is nocache documented? I don't see it in mount_nullfs(8), >> | mount(8) or nullfs(5). >> >> I didn't find it but it is in: >> src/sys/fs/nullfs/null_vfsops.c: if (vfs_getopt(mp->mnt_optnew, >> "nocache", NULL, NULL) == 0 || >> >> Also some file systems disable it via MNTK_NULL_NOCACHE > > Does the attached diff look ok? > >> | I tried a nullfs mount with nocache and it doesn't show up in the >> | output of "mount". >> >> Yep, I saw that as well. I could tell by dropping into ddb and then >> do a show mount on the FS and look at the count. That is why I added >> the vnode count to mount -v so I could see the usage without dropping >> into ddb. > > 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 ? 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. -- Mateusz Guzik <mjguzik gmail.com>
