> -----Original Message----- > From: Federico Motta [mailto:federico@xxxxxxxxx] > Sent: Friday, November 9, 2018 3:31 AM > To: Sitsofe Wheeler <sitsofe@xxxxxxxxx> > Cc: Jeff Furlong <jeff.furlong@xxxxxxx>; Elliott, Robert (Persistent Memory) <elliott@xxxxxxx>; fio > <fio@xxxxxxxxxxxxxxx>; Paolo Valente <paolo.valente@xxxxxxxxxx>; mark.brown@xxxxxxxxxx; > linus.walleij@xxxxxxxxxx; ulf.hansson@xxxxxxxxxx > Subject: Re: rand-read: increasing iodepth makes throughput drop > >> On 10/31/18 3:19 PM, Federico Motta wrote: > >> ... > >>> Is it possible to ask fio a measure of "how much device internal > >> queues are filled"? > >>> If yes, with which option(s)? > >>> If not, do you know some other tools or procedures which can tell us that? > >> > >> Does somebody has ideas about that ^ ? > > > > ...I think iostat produces similar output to that too... > > > > Actually I was wondering if a more direct or low level measure exists, > but since I don't even know if that is possible I think the fio "util" > percentage could be a good trade-off between "a low level measure" and > "no measure available". In linux, iostat provides some statistics, and there are lots of more detailed queuing statistics in sysfs. Some are provided by the block layer; some by the SCSI midlayer (for SCSI devices); some by the low-level driver (like hpsa). # nr_requests, the block layer request queue depth /sys/block/$device/queue/nr_requests # queue_depth, the SCSI midlayer queue depth /sys/block/$device/device/queue_depth # can_queue sets the initial request queue size /sys/class/scsi_host/$scsi_host/can_queue # cmd_per_lun sets the initial queue_depth /sys/class/scsi_host/$scsi_host/cmd_per_lun # host_busy indicates how many commands are queued by the SCSI layer /sys/class/scsi_host/$scsi_host/host_busy # host_blocked indicates the host is blocking all IOs /sys/class/scsi_host/$scsi_host/host_blocked # hpsa ioaccel commands outstanding /sys/block/$device/device/hpsa_ioaccel_cmds_out # hpsa physical drive queue depth /sys/block/$device/device/hpsa_queue_depth # hpsa commands_outstanding from submission to completion /sys/class/scsi_host/$scsi_host/commands_outstanding There are a bunch of blk-mq stats too, some only shown if debugfs is enabled.
