Date: Fri, 2 Oct 2009 16:38:24 -0700 From: Artem Belevich <fbsdlist@src.cx> To: Pawel Jakub Dawidek <pjd@freebsd.org> Cc: freebsd-fs@freebsd.org Subject: Re: ARC size constantly shrinks, then ZFS slows down extremely Message-ID: <ed91d4a80910021638r72213389uf0767b9bb523b7d9@mail.gmail.com> In-Reply-To: <20091002184526.GA1660@garage.freebsd.pl> References: <4AC1E540.9070001@fsn.hu> <4AC5B2C7.2000200@fsn.hu> <20091002184526.GA1660@garage.freebsd.pl>
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With the patch, if vfs.zfs.arc_min is set high enough, the system locks up. On a box with 8G or RAM I had arc_min=3D6G and arc_max=3D7G. Once ARC grew to ~5.8G as reported by kstat.zfs.misc.arcstats.size, number of wired pages grew to ~7400MB and the processes got stuck in 'vmwait' state. I had to reboot in order to recover. On one hand setting arc_min can be considered a pilot error. On the other, it may be a good idea to allow system to reclaim memory from ARC even if ARC is smaller than arc_min if the system really really needs it. The question is how to define "really needs it". On a side note, it appears that wired page count tends to be substantially larger than ARC size. I.e. in my case if ARC size grows to 6G, wired page count is about 1.5G bigger. Perhaps we should allow reclaiming memory --Artem On Fri, Oct 2, 2009 at 11:45 AM, Pawel Jakub Dawidek <pjd@freebsd.org> wrot= e: > On Fri, Oct 02, 2009 at 09:59:03AM +0200, Attila Nagy wrote: >> Backing out this change from the 8-STABLE kernel: >> http://svn.freebsd.org/viewvc/base/head/sys/cddl/contrib/opensolaris/uts= /common/fs/zfs/arc.c?r1=3D191901&r2=3D191902 >> >> makes it survive about half and hour of IMAP searching. Of course only >> time will tell whether this helps in the long run, but so far 10/10 >> tries succeeded to kill the machine with this method... > > Could you try this patch: > > =A0 =A0 =A0 =A0http://people.freebsd.org/~pjd/patches/arc.c.4.patch > > -- > Pawel Jakub Dawidek =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 http://ww= w.wheel.pl > pjd@FreeBSD.org =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 http:= //www.FreeBSD.org > FreeBSD committer =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 Am I Ev= il? Yes, I Am! >
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