Messages in this thread | | | Date | Thu, 13 Dec 2012 17:48:06 -0800 | From | Andy Lutomirski <> | Subject | Re: [PATCH 4/4] block: Optionally snapshot page contents to provide stable pages during write |
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On 12/13/2012 12:08 AM, Darrick J. Wong wrote: > Several complaints have been received regarding long file write latencies when > memory pages must be held stable during writeback. Since it might not be > acceptable to stall programs for the entire duration of a page write (which may > take many milliseconds even on good hardware), enable a second strategy wherein > pages are snapshotted as part of submit_bio; the snapshot can be held stable > while writes continue. > > This provides a band-aid to provide stable page writes on jbd without needing > to backport the fixed locking scheme in jbd2. A mount option is added to ext4 > to allow administrators to enable it there.
I'm a bit confused as to what it has to do with ext3. Wouldn't this be useful as a mount option everywhere, though?
If this becomes widely used, would it be better to snapshot on wait_for_stable_page instead of on io submission?
FWIW, I'm about to pound pretty hard on this whole patchset on a box that doesn't need stable pages. I'll let you know how it goes.
--Andy
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