Re: [PATCH 0/5] blk-mq/scsi-mq: support global tags & introduce force_blk_mq

Hannes Reinecke
2018-02-07T06:50:21Z

Hi all,

[ .. ]
>>
>> Could you share us your patch for enabling global_tags/MQ on
> megaraid_sas
>> so that I can reproduce your test?
>>
>>> See below perf top data. "bt_iter" is consuming 4 times more CPU.
>>
>> Could you share us what the IOPS/CPU utilization effect is after
> applying the
>> patch V2? And your test script?
> Regarding CPU utilization, I need to test one more time. Currently system
> is in used.
>
> I run below fio test on total 24 SSDs expander attached.
>
> numactl -N 1 fio jbod.fio --rw=randread --iodepth=64 --bs=4k
> --ioengine=libaio --rw=randread
>
> Performance dropped from 1.6 M IOPs to 770K IOPs.
>
This is basically what we've seen with earlier iterations.

>>
>> In theory, it shouldn't, because the HBA only supports HBA wide tags,
>> that means the allocation has to share a HBA wide sbitmap no matte>> if global tags is used or not.
>>
>> Anyway, I will take a look at the performance test and data.
>>
>>
>> Thanks,
>> Ming
>
>
> Megaraid_sas version of shared tag set.
>
Whee; thanks for that.

I've just finished a patchset moving megarai_sas_fusion to embedded
commands (and cutting down the size of 'struct megasas_cmd_fusion' by
half :-), so that will come in just handy.

Will give it a spin.

Cheers,

Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@suse.de +49 911 74053 688
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