On Fri 30-07-10 16:20:25, Christoph Hellwig wrote: > On Fri, Jul 30, 2010 at 05:44:08PM +0400, Vladislav Bolkhovitin wrote: > > Yes, but why not to make step further and allow to completely eliminate > > the waiting/draining using ORDERED requests? Current advanced storage > > hardware allows that. > > There is a few caes where we could do that - the fsync without metadata > changes above would be the prime example. But there's a lot lower > hanging fruit until we get to the point where it's worth trying. Umm, I don't understand you. I think that fsync in particular is an example where you have to wait and issue cache flush if the drive has volatile write cache. Otherwise you cannot promise to the user data will be really on disk in case of crash. So no ordering helps you. And if you are speaking about a drive without volatile write caches, then fsync without metadata changes is just trivial and you don't need any ordering. 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
