On Wed 11-05-11 01:12:13, OGAWA Hirofumi wrote: > Jan Kara <jack@xxxxxxx> writes: > > >> Did you already consider, to copy only if page was writeback (like > >> copy-on-write)? I.e. if page is on I/O, copy, then switch the page for > >> writing new data. > > Yes, that was considered as well. We'd have to essentially migrate the > > page that is under writeback and should be written to. You are going to pay > > the cost of page allocation, copy, increased memory & cache pressure. > > Depending on your backing storage and workload this may or may not be better > > than waiting for IO... > > Maybe possible, but you really think on usual case just blocking is > better? Define usual case... As Christoph noted, we don't currently have a real practical case where blocking would matter (since frequent rewrites are rather rare). So defining what is usual when we don't have a single real case is kind of tough ;) Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
