Re: Speed improvements in ZFS

Am 2023-08-21 10:53, schrieb Konstantin Belousov:
> On Mon, Aug 21, 2023 at 08:19:28AM +0200, Alexander Leidinger wrote:
>> Am 2023-08-20 23:17, schrieb Konstantin Belousov:
>> > On Sun, Aug 20, 2023 at 11:07:08PM +0200, Mateusz Guzik wrote:
>> > > On 8/20/23, Alexander Leidinger <Alexander@leidinger.net> wrote:
>> > > > Am 2023-08-20 22:02, schrieb Mateusz Guzik:
>> > > >> On 8/20/23, Alexander Leidinger <Alexander@leidinger.net> wrote:
>> > > >>> Am 2023-08-20 19:10, schrieb Mateusz Guzik:
>> > > >>>> On 8/18/23, Alexander Leidinger <Alexander@leidinger.net> wrote:
>> > > >>>
>> > > >>>>> I have a 51MB text file, compressed to about 1MB. Are you interested
>> > > >>>>> to
>> > > >>>>> get it?
>> > > >>>>>
>> > > >>>>
>> > > >>>> Your problem is not the vnode limit, but nullfs.
>> > > >>>>
>> > > >>>> https://people.freebsd.org/~mjg/netchild-periodic-find.svg
>> > > >>>
>> > > >>> 122 nullfs mounts on this system. And every jail I setup has several
>> > > >>> null mounts. One basesystem mounted into every jail, and then shared
>> > > >>> ports (packages/distfiles/ccache) across all of them.
>> > > >>>
>> > > >>>> First, some of the contention is notorious VI_LOCK in order to do
>> > > >>>> anything.
>> > > >>>>
>> > > >>>> But more importantly the mind-boggling off-cpu time comes from
>> > > >>>> exclusive locking which should not be there to begin with -- as in
>> > > >>>> that xlock in stat should be a slock.
>> > > >>>>
>> > > >>>> Maybe I'm going to look into it later.
>> > > >>>
>> > > >>> That would be fantastic.
>> > > >>>
>> > > >>
>> > > >> I did a quick test, things are shared locked as expected.
>> > > >>
>> > > >> However, I found the following:
>> > > >>         if ((xmp->nullm_flags & NULLM_CACHE) != 0) {
>> > > >>                 mp->mnt_kern_flag |=
>> > > >> lowerrootvp->v_mount->mnt_kern_flag &
>> > > >>                     (MNTK_SHARED_WRITES | MNTK_LOOKUP_SHARED |
>> > > >>                     MNTK_EXTENDED_SHARED);
>> > > >>         }
>> > > >>
>> > > >> are you using the "nocache" option? it has a side effect of xlocking
>> > > >
>> > > > I use noatime, noexec, nosuid, nfsv4acls. I do NOT use nocache.
>> > > >
>> > >
>> > > If you don't have "nocache" on null mounts, then I don't see how this
>> > > could happen.
>> >
>> > There is also MNTK_NULL_NOCACHE on lower fs, which is currently set for
>> > fuse and nfs at least.
>> 
>> 11 of those 122 nullfs mounts are ZFS datasets which are also NFS 
>> exported.
>> 6 of those nullfs mounts are also exported via Samba. The NFS exports
>> shouldn't be needed anymore, I will remove them.
> By nfs I meant nfs client, not nfs exports.

No NFS client mounts anywhere on this system. So where is this exclusive 
lock coming from then...
This is a ZFS system. 2 pools: one for the root, one for anything I need 
space for. Both pools reside on the same disks. The root pool is a 3-way 
mirror, the "space-pool" is a 5-disk raidz2. All jails are on the 
space-pool. The jails are all basejail-style jails.

Bye,
Alexander.

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