Date: Wed, 16 Jan 2013 08:42:45 +0100 From: Nicolas Rachinsky <fbsd-mas-0@ml.turing-complete.org> To: Steven Hartland <killing@multiplay.co.uk> Cc: freebsd-fs <freebsd-fs@freebsd.org> Subject: Re: slowdown of zfs (tx->tx) Message-ID: <20130116074245.GB47781@mid.pc5.i.0x5.de> In-Reply-To: <00F86FD0E85D4EEEA1A01E115497F022@multiplay.co.uk> References: <CAFqOu6gWpMsWN0pTBiv10WfwyGWMfO9GzMLWTtcVxHixr-_i3Q@mail.gmail.com> <20130114094010.GA75529@mid.pc5.i.0x5.de> <CAFqOu6hxfGt_M6Jo9qWeifDz9YnNc_Bd9H-GEe4RYtutaPvH5w@mail.gmail.com> <20130114195148.GA20540@mid.pc5.i.0x5.de> <CAFqOu6jwJ4qhbOovN_NhzusdQJvrbvUC3g93sziR=Uw99SGenw@mail.gmail.com> <20130114214652.GA76779@mid.pc5.i.0x5.de> <CAFqOu6jKX-Ks6C1RK5GwZ51ZVUSnGSe7S99_EfK%2BfwLPjAFFYw@mail.gmail.com> <20130115224556.GA41774@mid.pc5.i.0x5.de> <CAFqOu6jJnWdbikPmE1-UML5i_x7meF%2BiyY=9WBRyv2j7AeOaSg@mail.gmail.com> <00F86FD0E85D4EEEA1A01E115497F022@multiplay.co.uk>
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* Steven Hartland <killing@multiplay.co.uk> [2013-01-16 00:57 -0000]: > > ----- Original Message ----- From: "Artem Belevich" > <art@freebsd.org> > To: "Nicolas Rachinsky" <fbsd-mas-0@ml.turing-complete.org> > Cc: "freebsd-fs" <freebsd-fs@freebsd.org> > Sent: Wednesday, January 16, 2013 12:16 AM > Subject: Re: slowdown of zfs (tx->tx) > > > >It appears that lots of threads are stuck in > >metaslab_activate->space_map_load_wait path. This sounds like CR# > >6876962 in Solaris: "degraded write performance with threads held up > >by space_map_load_wait(). This bug is fixed in patch 147440-05, -06 or > >-07, which is current and contains the fix." Alas, I could not find > >specifics on how the issue got fixed and whether the same fix is > >present in illumos and FreeBSD. > > That would tend to indicate its blocking on write. If this is the case > yet the rsync is copying from this box, with little else doing writes > it could be atime which is causing the issue. I was probably misformulating my mail. The rsync writes to the local zpool. > A test for this would be to use the following to disable atime and see > if that helps: > zfs set atime=off [filesystem] > > Also out of interest does the pool have many snapshots? There are 115 filesystems. 84 of these have between 10 and 20 snapshots. Nicolas -- http://www.rachinsky.de/nicolas
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