On Thu, Mar 29, 2012 at 11:30 AM, Jeff Moyer <jmoyer@xxxxxxxxxx> wrote: > Chuck Tuffli <ctuffli@xxxxxxxxx> writes: > >> On Thu, Mar 29, 2012 at 10:14 AM, Chris Worley <worleys@xxxxxxxxx> wrote: >>> Sequential merging? Try "randread" instead. >> >> Great suggestion. Doing some additional analysis, it does appear that >> IO's are probably getting merged as I see individual IO requests on >> the wire of 2-4KB. >> >> Googling around this area seems to suggest this kernel behavior isn't >> something I can disable. So if I honest to goodness *only* want 512B >> IO, is ioengine=sg the best route? > > Try setting /sys/block/sdX/queue/nomerges to 2. That should completely > disable merging. Jeff - I upgrade to a 3.0 series kernel and set nomerges to 2 and now all the tools agree on the IOPs number. Thanks! ---chuck -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
