Messages in this thread | | | Date | Sat, 21 Mar 2009 12:14:00 +0100 | From | Jens Axboe <> | Subject | Re: [PATCH] block: forbid to re-enable I/O stat accounting |
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On Sat, Mar 21 2009, Andrew Morton wrote: > > Please fix your email headers - what I received was > > From: Jerome Marchand <jmarchan@redhat.com> > To: unlisted-recipients:;;@imap1.linux-foundation.org (no To-header on input) > Cc: Jens Axboe <axboe@kernel.dk>
Ditto, I didn't think anyone else got it. At least noone else got my reply :-)
> On Thu, 19 Mar 2009 11:36:50 +0100 Jerome Marchand <jmarchan@redhat.com> wrote: > > > When we stop I/O stat accounting we stop to update the in-flight > > requests counter and we need this counter to be reliable for > > accounting I/O stats. Unfortunately updating in_flight field may > > affect performance. So, until we have a better solution, just forbid > > to re-enable I/O stat accounting after it has been disabled. > > hm. Is it really so hard to just quiesce the device until all in-flight > requests have drained? freeze_bdev() might be a suitable starting point?
That was my suggestion as well, we really need to be able to turn it back on again. Ideally, I'd like iostat and friends to turn it on/off when somebody does the monitoring. A one-way street option is not very nice.
-- Jens Axboe
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