Re: Speed improvements in ZFS

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.

Bye,
Alexander.

-- 
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