On Thu, Aug 21, 2008 at 04:04:18PM +1000, Dave Chinner wrote: > One thing I just found out - my old *laptop* is 4-5x faster than the > 10krpm scsi disk behind an old cciss raid controller. I'm wondering > if the long delays in dispatch is caused by an interaction with CTQ > but I can't change it on the cciss raid controllers. Are you using > ctq/ncq on your machine? If so, can you reduce the depth to > something less than 4 and see what difference that makes? I don't think that's going to make a difference when using CFQ. I did some tests that showed that CFQ would never issue more than one IO at a time to a drive. This was using sixteen userspace threads, each doing a 4k direct I/O to the same location. When using noop, I would get 70k IOPS and when using CFQ I'd get around 40k IOPS. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
