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Subject: Re: [dm-devel] [PATCH 1/1] block: Convert hd_struct in_flight from
 atomic to percpu
To: Ming Lei <tom.leiming@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>,
        linux-block <linux-block@vger.kernel.org>,
        "open list:DEVICE-MAPPER (LVM)" <dm-devel@redhat.com>,
        Mike Snitzer <snitzer@redhat.com>,
        Alasdair Kergon <agk@redhat.com>
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From: Brian King <brking@linux.vnet.ibm.com>
Date: Tue, 4 Jul 2017 15:58:00 -0500
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On 07/03/2017 08:20 PM, Ming Lei wrote:
>> Right. So the two modes I'm running in are:
>>
>> 1. 80 null_blk devices, each with one submit_queue, with one fio job per null_blk device,
>>    so 80 threads total. 80 logical CPUs
>> 2. 1 null_blk device, with 80 submit_queues, 80 fio jobs, 80 logical CPUs.
>>
>> In theory, the two should result in similar numbers.
>>
>> Here are the commands and fio configurations:
>>
>> Scenario #1
>> modprobe null_blk submit_queues=80 nr_devices=1 irqmode=0
>>
>> FIO config:
>> [global]
>> buffered=0
>> invalidate=1
>> bs=4k
>> iodepth=64
>> numjobs=80
>> group_reporting=1
>> rw=randrw
>> rwmixread=100
>> rwmixwrite=0
>> ioengine=libaio
>> runtime=60
>> time_based
>>
>> [job1]
>> filename=/dev/nullb0

> 
> IMO it should be more reasonable to use single null_blk with 80 queues
> via setting submit_queues as 80 than simply 80 null_blks.  So suggest to switch
> to test 80 queues in your future test.

That should be what my Scenario #1 covers. 

Thanks,

Brian

-- 
Brian King
Power Linux I/O
IBM Linux Technology Center