Date: Tue, 18 Mar 2014 05:16:44 -0700 From: Adrian Chadd <adrian@freebsd.org> To: Matthew Seaman <matthew@freebsd.org> Cc: FreeBSD Mailing Lists <freebsd-performance@freebsd.org> Subject: Re: FreeBSD 10 and PostgreSQL 9.3 scalability issues Message-ID: <CAJ-Vmok-6xXYtAHJ2W4oSh38ang35MzRzFdaXkrDgyBCU3AceQ@mail.gmail.com> In-Reply-To: <53283557.4070105@freebsd.org> References: <5327B9B7.3050103@gmail.com> <53283557.4070105@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
Hi, the pgsql testing done has been analysed by a few developers. The TL;DR version is that there's significant lock contention in the VM / mmap path and it sticks out like a sore thumb when one does lock profiling. -a On 18 March 2014 05:00, Matthew Seaman <matthew@freebsd.org> wrote: > On 03/18/14 03:12, Petr Janda wrote: >> ust want to share these pgbench results done by DragonFlyBSD, and would >> like some input on why these numbers look so bad and what can be done to >> improve (ie. kernel tunables etc) the performance. >> >> http://lists.dragonflybsd.org/pipermail/users/attachments/20140310/4250b961/attachment-0001.pdf > > Using ZFS as the backing for a RDBMS without: > > * Separate (fast) L2ARC devices > * Tuning the ZFS block size to match the postgres IO block size > * Setting primarycache to metadata > * Tuning the ARC max so ZFS doesn't eat all the RAM > * probably other things I can remember off-hand. > > That's what is wrong. ZFS is known to work particularly badly at the > sort of small random IOs that RDBMSes generate (mostly because of the > copy-on-write thing) without special tuning and extra hardware for > caches. ie. You can't construct a fair test of database performance > against other OSes/filesystems if you restrict yourself to using exactly > the same hardware. > > Basically, install the FreeBSD box on UFS2 and try again. > > Cheers, > > Matthew > >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAJ-Vmok-6xXYtAHJ2W4oSh38ang35MzRzFdaXkrDgyBCU3AceQ>