All, I recently filed https://github.com/axboe/fio/issues/1483 on github describing my usage of multiple concurrent jobs to split random read and random write so I can have a different number of reader and writer threads. I was informed that what I actually want is to use "flow=" to specify the ratio of activity between jobs. My issue while testing the use of flow, is that it seems to be off by a factor of 10x. For example, the following has two jobs, one for readers and one for writers. The writer, as can be seen, has "numjobs" set to 8, while the reader has "numjobs" set to 64. Flow is set to "100" for reader, and "1" for writer. But from the output below we can see the actual split is more like 786 to 1. Jobs: 72 (f=72): [w(8),r(64)][26.6%][r=1254MiB/s,w=1632KiB/s][r=321k,w=408 IOPS][eta 44m:11s] Should I be dividing the flow value by the ratio of "numjobs" as well? The command running obviously has an 8:1 ratio of readers to writers, and I've defined a 100:1 ratio in the value of "flow", so am I actually seeing an 800:1 here? I suspect I'm missing a key piece of information, but the documentation doesn't explicitly call this out. The line that makes me think I may need to adjust for "numjobs" within each job is "The flow parameter stands for how much should be added or subtracted to the flow counter on each iteration of the main I/O loop.". This makes me suspect that each of the threads spawned under a job definition is spawned with it's own 100:1 ratio, and since there's an 8:1 numjobs ratio, I end up seeing the above. The command, in total, is below. fio --output=fio-logs/m2test-01/20221102/manual-flow-test.write-1.qd-32/fio.manual-flow-test.log \ --exitall_on_error --bs=4Ki --direct=1 --fadvise_hint=random --filename=/mnt/testing/fio \ --group_reporting=1 --iodepth=32 --ioengine=libaio --ioscheduler=mq-deadline --log_avg_msec=1000 \ --log_compression=1m --log_store_compressed=1 --ramp_time=10 --randrepeat=0 --runtime=1h --thread \ --time_based --write_bw_log=fio-logs/m2test-01/20221102/manual-flow-test.write-1.qd-32/fio-stress \ --write_iops_log=fio-logs/m2test-01/20221102/manual-flow-test.write-1.qd-32/fio-stress \ --write_lat_log=fio-logs/m2test-01/20221102/manual-flow-test.write-1.qd-32/fio-stress \ --name=writer --new_group --stonewall --numjobs=8 --rw=randwrite --flow=1 --exitall \ --name=reader --new_group --numjobs=64 --rw=randread --flow=100 Thanks for any advice, Tom
