Bob Friesenhahn
Tue, 30 Jun 2009 12:26:01 -0700
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 = 0x18000000CPU 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
