Re: About scsi device queue depth

John Garry
2021-01-12T17:46:22Z

>>>> sdev qdepth fio number jobs* 1 10 20
>>>> 16 1590 1654 1660
>>>> 32 1545 1646 1654
>>>> 64 1436 1085 1070
>>>> 254 (default) 1436 1070 1050
>>> What does the performance number mean? IOPS or others? What is the fio
>>> io test? random IO or sequential IO?
>> So those figures are x1K IOPs read performance; so 1590, above, is 1.59M
>> IOPs read. Here's the fio script:
>>
>> [global]
>> rw=read
>> direct=1
>> ioengine=libaio
>> iodepth=40
>> numjobs=20
>> bs=4k
>> ;size=10240000m
>> ;zero_buffers=1
>> group_reporting=1
>> ;ioscheduler=noop
>> ;cpumask=0xffe
>> ;cpus_allowed=1-47
>> ;gtod_reduce=1
>> ;iodepth_batch=2
>> ;iodepth_batch_complete=2
>> runtime=60
>> ;thread
>> loops = 10000
> Is there any effect on random read IOPS when you decrease sdev queue
> depth? For sequential IO, IO merge can be enhanced by that way.
>

Hi Ming,

fio randread results:

fio queue depth 40
sdev qdepth fio number jobs* 1 10 20
8 1308K 831K 814K
16 1435K 1073K 988K
32 1438K 1065K 990K
64 1432K 1061K 1020K
254 (default) 1439K 1099K 1083K

fio queue depth 128
sdev qdepth fio number jobs* 1 10 20
8 1310K 860K 849K
16 1435K 1048K 958K
32 1438K 1140K 951K
64 1438K 1065K 953k
254 (default) 1439K 1140K 1056K

So randread goes in the opposite direction (to read wrt queue depth).

Thanks,
John