From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: fio and total latency percentile References: <53cbc635-d9a3-6ef3-3634-309db0fe03d5@intel.com> <0c340072-33cc-2171-c149-1ef0b8f94fce@kernel.dk> <2fea8192-2373-a27e-c484-07fe5854aab7@kernel.dk> <112A412BB11A1242B37129D931BCE534734BD274@fmsmsx116.amr.corp.intel.com> From: Jens Axboe Message-ID: <296b0e8b-2612-d29a-d739-ae829b4adcb1@kernel.dk> Date: Thu, 14 Sep 2017 10:46:08 -0600 MIME-Version: 1.0 In-Reply-To: <112A412BB11A1242B37129D931BCE534734BD274@fmsmsx116.amr.corp.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit To: "Jiang, Dave" Cc: "fio@vger.kernel.org" , "Williams, Dan J" List-ID: On 09/14/2017 10:45 AM, Jiang, Dave wrote: > > >> -----Original Message----- >> From: Jens Axboe [mailto:axboe@kernel.dk] >> Sent: Wednesday, September 13, 2017 9:09 PM >> To: Jiang, Dave >> Cc: fio@vger.kernel.org; Williams, Dan J >> 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! Good to hear! Thanks for testing. -- Jens Axboe