Hi zfs-discuss, I have some questions about throttling on ZFS 1) I know that throttling is activating while one sync is waiting for another. (http://blogs.sun.com/roller/page/roch?entry=the_dynamics_of_zfs) Is it possible to throttle only selected processes (e.g. nfsd) ? 2) How can I obtain some statistics about it? I want to know how often throttling is activating on my host etc. 3) Is it possible to change 5-seconds interval of sync activation? (some mdb''s magic tricks? :) ) 4) How can I turn off throttling? Best regards, Andrzej This message posted from opensolaris.org
Hello Andrzej,
Thursday, June 22, 2006, 11:30:23 AM, you wrote:
AB> Hi zfs-discuss,
AB> I have some questions about throttling on ZFS
AB> 1) I know that throttling is activating while one sync is waiting
AB> for another.
AB> (http://blogs.sun.com/roller/page/roch?entry=the_dynamics_of_zfs)
AB> Is it possible to throttle only selected processes (e.g. nfsd) ?
If I understand it correctly you can''t - throttling is for all
transactions to a pool.
AB> 2) How can I obtain some statistics about it? I want to know how
AB> often throttling is activating on my host etc.
AB> 3) Is it possible to change 5-seconds interval of sync
AB> activation? (some mdb''s magic tricks? :) )
txg_time/W
AB> 4) How can I turn off throttling?
In a way you can - see "Re: [zfs-discuss] fdsync(5, FSYNC) problem and
ZFS" thread and look for hot to disable ZIL.
--
Best regards,
Robert mailto:rmilkowski at task.gda.pl
http://milek.blogspot.com
Robert Milkowski writes: > Hello Andrzej, > > Thursday, June 22, 2006, 11:30:23 AM, you wrote: > > AB> Hi zfs-discuss, > > AB> I have some questions about throttling on ZFS > > AB> 1) I know that throttling is activating while one sync is waiting > AB> for another. > AB> (http://blogs.sun.com/roller/page/roch?entry=the_dynamics_of_zfs) > AB> Is it possible to throttle only selected processes (e.g. nfsd) ? > NFS usually needs to sync a lot so that has a throttling effect on it''s own. I''m not sure this is the solution to your problem. There are other ways to throttle NFS such as reducing the number of deamons (and maybe CPU binding ?). > If I understand it correctly you can''t - throttling is for all > transactions to a pool. Yep. Do I sense in the question that throttling is considered armfull ? In my book throttling is how we match I/O throughput and application throughput. You can defer it a little or change the granularity but you can''t avoid it. > > > AB> 2) How can I obtain some statistics about it? I want to know how > AB> often throttling is activating on my host etc. I think calls to txg_wait_open() should do it. > > AB> 3) Is it possible to change 5-seconds interval of sync > AB> activation? (some mdb''s magic tricks? :) ) > > txg_time/W > > > AB> 4) How can I turn off throttling? Maybe large txg_time would do it. Mostly likely would degrade or render your system unusable. > > In a way you can - see "Re: [zfs-discuss] fdsync(5, FSYNC) problem and > ZFS" thread and look for hot to disable ZIL. ZIL is something else than the txg. So even that will not work. Disabling the ZIL would actually increase likelyhood of txg throttling. -r > > -- > Best regards, > Robert mailto:rmilkowski at task.gda.pl > http://milek.blogspot.com > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss at opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss