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. -- 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
