On Thu, 2010-07-29 at 22:03 +0200, Christoph Hellwig wrote: > On Thu, Jul 29, 2010 at 02:59:51PM -0500, James Bottomley wrote: > > That's basically everything FUA ... you might just as well switch your > > cache to write through and have done. > > > > This, by the way, is one area I'm hoping to have researched on SCSI > > (where most devices do obey the caching directives). Actually see if > > write through without flush barriers is faster than writeback with flush > > barriers. I really suspect it is. > > We have done the research and at least for XFS a write through cache > actually is faster for many workloads. Ric always has workloads where > the cache is faster, though - mostly doing lots of small file write > kind of setups. There's lies, damned lies and benchmarks .. but what I was thinking is could we just do the right thing? SCSI exposes (in sd) the interfaces to change the cache setting, so if the customer *doesn't* specify barriers on mount, could we just flip the device to write through it would be more performant in most use cases. James -- 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
