On Sat, 2009-08-15 at 09:22 -0400, Mark Lord wrote: > James Bottomley wrote: > > > > This means you have to drain the outstanding NCQ commands (stalling the > > device) before you can send a TRIM. If we do this for every discard, > > the performance impact will be pretty devastating, hence the need to > > coalesce. It's nothing really to do with device characteristics, it's > > an ATA protocol problem. > .. > > I don't think that's really much of an issue -- we already have to do > that for cache-flushes whenever barriers are enabled. Yes it costs, > but not too much. That's not really what the enterprise is saying about flush barriers. True, not all the performance problems are NCQ queue drain, but for a steady workload they are significant. James -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
