On Thu, Oct 10 2013, Juergen Salk wrote: > * Jens Axboe <axboe@xxxxxxxxx> [130925 15:01]: > > > >>> --- snip --- > > >>> [global] > > >>> ioengine=sync > > >>> direct=0 > > >>> bssplit=19k/25:177k/15:350k/60 > > >>> size=100m > > >>> numjobs=4 > > >>> directory=/tmp > > >>> > > >>> [work] > > >>> rw=randread > > >>> --- snip --- > > >>> > > >>> $ fio jobfile.fio >fio.out > > >>> $ grep io= fio.out > > >>> read : io=199968KB, bw=4892.6KB/s, iops=27, runt= 40872msec > > >>> read : io=200062KB, bw=5083.5KB/s, iops=28, runt= 39359msec > > >>> read : io=200156KB, bw=4989.1KB/s, iops=27, runt= 40112msec > > >>> read : io=199940KB, bw=4492.4KB/s, iops=24, runt= 44507msec > > >>> READ: io=800126KB, aggrb=17977KB/s, minb=4492KB/s, maxb=5083KB/s, mint=39359msec, maxt=44507msec > > >>> > > >>> [...] > > >>> > > >>> I am probably missing something obvious, but why does the job file > > >>> above result in 200 MB read by every process? > > >> > > >> It should not, that's definitely a bug. I'm guessing it's triggered by > > >> the strange block sizes being used. Can you see if adding: > > >> > > >> random_generator=lfsr > > >> > > >> helps? > > > > > > Thanks for your response, Jens. Yes it does. It's a bit confusing > > > though, as the man page says "LFSR only works with single block > > > sizes, not with workloads that use multiple block sizes. If used > > > with such a workload, fio may read or write some blocks multiple > > > times." Shouldn't this be read as "Don't use LFSR with mixed > > > block sizes."? > > > > That is correct, my suspicion is just that the current logic around when > > to decide to run another loop is wrong. Right now we just look to see if > > the remainder is smaller than the max block size, but that doesn't mean > > that we necessarily have that big of a free chunk available. I suspect > > you are hitting this because of the odd block sizes. > > > > > I am sorry to keep on harping on the matter, but I am planning to > > > use fio for simulating file sizes where total runtime will > > > become a serious issue. And these simulations will definitely > > > involve strange mixed block sizes ... > > > > No worries, it's definitely a bug. Checking for a fix right now... > > Just out of curiosity: Is there any news on that issue? I got it mostly fixed, but it gets quite complicated. Traveling this week, will hopefully have some time to wrap it up. -- Jens Axboe -- 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
