Date: Mon, 3 May 2010 04:01:00 -0700 From: Jeremy Chadwick <freebsd@jdc.parodius.com> To: Giulio Ferro <auryn@zirakzigil.org> Cc: freebsd-stable@freebsd.org Subject: Re: Freebsd 8.0 kmem map too small Message-ID: <20100503110100.GA93137@icarus.home.lan> In-Reply-To: <4BDEA86E.3050109@zirakzigil.org> References: <4BDEA86E.3050109@zirakzigil.org>
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On Mon, May 03, 2010 at 12:41:50PM +0200, Giulio Ferro wrote: > NFS server amd64 Freebsd 8.0 recent (2 days ago) > > This server has been running for several months without problems. > Beginning last week, however, I'm experiencing panics (about 1 per day) > with the error in the subject > > Current settings: > > > vm.kmem_size_scale: 3 > vm.kmem_size_max: 329853485875 > vm.kmem_size_min: 0 > vm.kmem_size: 2764046336 > ... > hw.physmem: 8568225792 > hw.usermem: 6117404672 > hw.realmem: 9395240960 > ... > vfs.zfs.l2arc_noprefetch: 0 > vfs.zfs.l2arc_feed_secs_shift: 1 > vfs.zfs.l2arc_feed_secs: 1 > vfs.zfs.l2arc_headroom: 128 > vfs.zfs.l2arc_write_boost: 67108864 > vfs.zfs.l2arc_write_max: 67108864 > vfs.zfs.arc_meta_limit: 431882240 > vfs.zfs.arc_meta_used: 431874720 > vfs.zfs.arc_min: 215941120 > vfs.zfs.arc_max: 1727528960 > > > I've set nothing in either /boot/loader.conf or sysctl.conf > > > What should I do? You need to adjust vm.kmem_size to provide more space for the ARC. Below are ZFS-relevant entries in our /boot/loader.conf on production RELENG_8 systems with 8GB of RAM. The reason we set kmem_size to half our physical system memory is because I didn't want to risk other processes which use a larger maxdsiz/dfldsiz/maxssiz to potentially exhaust all memory. # Increase vm.kmem_size to allow for ZFS ARC to utilise more memory. vm.kmem_size="4096M" vfs.zfs.arc_max="3584M" # Disable ZFS prefetching # http://southbrain.com/south/2008/04/the-nightmare-comes-slowly-zfs.html # Increases overall speed of ZFS, but when disk flushing/writes occur, # system is less responsive (due to extreme disk I/O). # NOTE: 8.0-RC1 disables this by default on systems <= 4GB RAM anyway # NOTE: System has 8GB of RAM, so prefetch would be enabled by default. vfs.zfs.prefetch_disable="1" # Decrease ZFS txg timeout value from 30 (default) to 5 seconds. This # should increase throughput and decrease the "bursty" stalls that # happen during immense I/O with ZFS. # http://lists.freebsd.org/pipermail/freebsd-fs/2009-December/007343.html # http://lists.freebsd.org/pipermail/freebsd-fs/2009-December/007355.html vfs.zfs.txg.timeout="5" -- | Jeremy Chadwick jdc@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB |
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