Date: Fri, 17 Apr 2009 21:05:52 +0200 From: Bernd Walter <ticso@cicely7.cicely.de> To: Marius =?iso-8859-1?Q?N=FCnnerich?= <marius@nuenneri.ch> Cc: Alexander Leidinger <Alexander@leidinger.net>, ticso@cicely.de, fs@freebsd.org, current@freebsd.org Subject: Re: ZFS: unlimited arc cache growth? Message-ID: <20090417190551.GT11551@cicely7.cicely.de> In-Reply-To: <b649e5e0904170928p1568329bwb2f8a5f0f9b4f698@mail.gmail.com> References: <20090417145024.205173ighmwi4j0o@webmail.leidinger.net> <20090417141817.GR11551@cicely7.cicely.de> <b649e5e0904170928p1568329bwb2f8a5f0f9b4f698@mail.gmail.com>
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On Fri, Apr 17, 2009 at 06:28:29PM +0200, Marius Nünnerich wrote: > On Fri, Apr 17, 2009 at 16:18, Bernd Walter <ticso@cicely7.cicely.de> wrote: > > On Fri, Apr 17, 2009 at 02:50:24PM +0200, Alexander Leidinger wrote: > >> Hi, > >> > >> to fs@, please CC me, as I'm not subscribed. > >> > >> I monitored (by hand) a while the sysctls kstat.zfs.misc.arcstats.size > >> and kstat.zfs.misc.arcstats.hdr_size. Both grow way higher (at some > >> point I've seen more than 500M) than what I have configured in > >> vfs.zfs.arc_max (40M). > > > > My understanding about this is the following: > > vfs.zfs.arc_min/max are not used as min max values. > > They are used as high/low watermarks. > > If arc is more than max the arc a thread is triggered to reduce the > > arc cache until min, but in the meantime other threads can still grow > > arc so there is a race between them. > > Hmm, if this is true the ARC size should go down to arc_min once it > did grow past arc_max and no new data is coming along but I do not > observe such a thing here. It simply stays near but below arc_max here > all the time. I have only /home on ZFS with moderate load. I had a few ideas why this could be, but scanning complete sys showed no point at all where arc_min is used. There are formular to set this value, but that's all I find. -- B.Walter <bernd@bwct.de> http://www.bwct.de Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
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