On Tue, Jun 30, 2009 at 12:25 PM, Bob Friesenhahn<bfrie...@simple.dallas.tx.us> wrote: > On Mon, 29 Jun 2009, Lejun Zhu wrote: >> >> With ZFS write throttle, the number 2.5GB is tunable. From what I've read >> in the code, it is possible to e.g. set zfs:zfs_write_limit_override = >> 0x8000000 (bytes) to make it write 128M instead. > > This works, and the difference in behavior is profound. Now it is a matter > of finding the "best" value which optimizes both usability and performance. > A tuning for 384 MB: > > # echo zfs_write_limit_override/W0t402653184 | mdb -kw > zfs_write_limit_override: 0x30000000 = 0x18000000 > > CPU is smoothed out quite a lot and write latencies (as reported by a > zio_rw.d dtrace script) are radically different than before. > > Perfmeter display for 256 MB: > http://www.simplesystems.org/users/bfriesen/zfs-discuss/perfmeter-256mb.png > > Perfmeter display for 384 MB: > http://www.simplesystems.org/users/bfriesen/zfs-discuss/perfmeter-384mb.png > > Perfmeter display for 768 MB: > http://www.simplesystems.org/users/bfriesen/zfs-discuss/perfmeter-768mb.png > > Bob > -- > Bob Friesenhahn > bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ > GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss >
Maybe there could be a supported ZFS tuneable (per file system even?) that is optimized for 'background' tasks, or 'foreground'. Beyond that, I will give this tuneable a shot and see how it impacts my own workload. Thanks! -- Brent Jones br...@servuhome.net _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
