Date: Mon, 12 Jul 2010 19:38:18 +1000 From: Peter Jeremy <peterjeremy@acm.org> To: Richard Lee <ricky@csua.berkeley.edu> Cc: freebsd-stable@freebsd.org Subject: Re: Serious zfs slowdown when mixed with another file system (ufs/msdosfs/etc.). Message-ID: <20100712093818.GA27693@server.vk2pj.dyndns.org> In-Reply-To: <20100711182511.GA21063@soda.CSUA.Berkeley.EDU> References: <20100711182511.GA21063@soda.CSUA.Berkeley.EDU>
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--OgqxwSJOaUobr8KG Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2010-Jul-11 11:25:12 -0700, Richard Lee <ricky@csua.berkeley.edu> wrote: >But when almost all of the memory is taken by disk cache (of non-zfs >file system), ZFS disks start threshing like mad and the write >throughput goes down in 1-digit MB/second. It can go a lot lower than that... Yes, this is a known problem. The underlying problem is a disconnect between the ZFS cache (ARC) and the VM cache used by everything else, preventing ZFS reclaiming RAM from the VM cache. For several months, I was running a regular cron job that was a slightly fancier version of the perl one-liner. I have been using the attached arc.patch1 based on a patch written by Artem Belevich <fbsdlist@src.cx> (see http://pastebin.com/ZCkzkWcs ) for about a month. I have had reasonable success with it (and junked my cronjob) but have managed to wedge my system a couple of times whilst doing zfs send|recv. Whilst looking at that diff, I just noticed a nasty signed/unsigned bug that could bite in low memory conditions and have revised it to arc.patch2 (untested as yet). Independently, Martin Matuska <mm@FreeBSD.org> committed r209227 that corrects a number of ARC bugs reported on OpenSolaris. Whilst this patch doesn't add checks on "inactive" or "cache", some quick checks suggest it also helps (though I need to do further checks). See http://people.freebsd.org/~mm/patches/zfs/head-12636.patch --=20 Peter Jeremy --OgqxwSJOaUobr8KG Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.15 (FreeBSD) iEYEARECAAYFAkw64okACgkQ/opHv/APuIcWowCgiBc5ro8DGQfGRq4aafxxeUuu 6uUAn0IoSIvaaEfKUDncom1IrQ5NUakn =V4R+ -----END PGP SIGNATURE----- --OgqxwSJOaUobr8KG--
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