> -----Original Message----- > From: Jens Axboe [mailto:axboe@xxxxxxxxx] > Sent: Wednesday, September 13, 2017 9:09 PM > To: Jiang, Dave <dave.jiang@xxxxxxxxx> > Cc: fio@xxxxxxxxxxxxxxx; Williams, Dan J <dan.j.williams@xxxxxxxxx> > Subject: Re: fio and total latency percentile > > On 09/13/2017 10:03 PM, Jens Axboe wrote: > > On 09/13/2017 04:59 PM, Jens Axboe wrote: > >> On 09/07/2017 01:59 PM, Dave Jiang wrote: > >>> Jens, > >>> fio can display completion latency percentages via the percentile_list > >>> parameter. I can get p90 and p99 numbers for clat via > >>> percentile_list=90:99. Is there a way to get the overall latency for > >>> percentile? I'm interested in the total latency measurements for p90 and > >>> p99 while doing some measurements on the persistent memory block driver > >>> and playing around using DMA engines for transfer. > >> > >> If I understand correctly, you are using an IO engine that is async, and > >> you want the latency percentiles to reflect total IO time > >> (submission+completion), not just completion time? > >> > >> We can't currently do that, but it'd be trivial to do with an option of > >> some sort. Currently the percentile enable option is clat_percentile, > >> and it defaults to on. We could have a lat_percentile option that, if > >> enabled, would change the reporting to being total IO time. IOW: > >> > >> clat_percentile=1 Latency percentiles are completion latencies > >> lat_percentile=1 Latency percentiles are total IO time > >> > >> and have them be mutually exclusive. > > > > Something like the below. Please try it out and see if it works for you. > > Or just try current -git. I got cocky and just committed it. Works great! Exactly what I need. Thanks Jens! ��.n��������+%������w��{.n�������^n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�
