Date: Sun, 20 Aug 2023 22:02:31 +0200 From: Mateusz Guzik <mjguzik@gmail.com> To: Alexander Leidinger <Alexander@leidinger.net> Cc: current@freebsd.org Subject: Re: Speed improvements in ZFS Message-ID: <CAGudoHGPw0Dmnv6ont8JGyLsT7qv%2BQqAFZO3tKOpNo3eN%2BJgLQ@mail.gmail.com> In-Reply-To: <73f7c9d3db8f117deb077fb17b1e352a@Leidinger.net> References: <61ca9df1b15c0e5477ff51196d0ec073@Leidinger.net> <CAGudoHG5Fgg4184SsXhzqYRR7VPaBXZoirGvyRyJX5ihX5YG-A@mail.gmail.com> <ed1f82dd26d3cc9ec9cc16505109ec40@Leidinger.net> <CAGudoHEP8TrSzz0TL-PsOx0WNc7z3042wJk-jhhVwhTyJ0VEQQ@mail.gmail.com> <88e837aeb5a65c1f001de2077fb7bcbd@Leidinger.net> <4d60bd12b482e020fd4b186a9ec1a250@Leidinger.net> <CAGudoHE7RPcHpQEqKbzRM8cJcYKue17=iPVv8iOfZq03h22tTA@mail.gmail.com> <73f7c9d3db8f117deb077fb17b1e352a@Leidinger.net>
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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 -- Mateusz Guzik <mjguzik gmail.com>
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