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Date:   Mon, 25 Apr 2022 09:39:30 -0600
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To:     Guoqing Jiang <guoqing.jiang@linux.dev>, Xiao Ni <xni@redhat.com>
Cc:     open list <linux-kernel@vger.kernel.org>,
        linux-raid <linux-raid@vger.kernel.org>,
        Song Liu <song@kernel.org>,
        Christoph Hellwig <hch@infradead.org>,
        Stephen Bates <sbates@raithlin.com>,
        Martin Oliveira <Martin.Oliveira@eideticom.com>,
        David Sloan <David.Sloan@eideticom.com>
References: <20220420195425.34911-1-logang@deltatee.com>
 <CALTww28fwNpm0O_jc7-2Xr0JSX9i6F1kgoUQ8m_k6ZgPa1XxXw@mail.gmail.com>
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 <4094aed9-d22d-d14f-07a7-5abe599beeab@linux.dev>
From:   Logan Gunthorpe <logang@deltatee.com>
In-Reply-To: <4094aed9-d22d-d14f-07a7-5abe599beeab@linux.dev>
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Subject: Re: [PATCH v2 00/12] Improve Raid5 Lock Contention
Precedence: bulk


On 2022-04-24 02:00, Guoqing Jiang wrote:
> 
> 
> On 4/22/22 12:02 AM, Logan Gunthorpe wrote:
>>
>> On 2022-04-21 02:45, Xiao Ni wrote:
>>> Could you share the commands to get the test result (lock contention
>>> and performance)?
>> Sure. The performance we were focused on was large block writes. So we
>> setup raid5 instances with varying number of disks and ran the following
>> fio script directly on the drive.
>>
>> [simple]
>> filename=/dev/md0
>> ioengine=libaio
>> rw=write
>> direct=1
>> size=8G
>> blocksize=2m
>> iodepth=16
>> runtime=30s
>> time_based=1
>> offset_increment=8G
>> numjobs=12
>> ￼
>> (We also played around with tuning this but didn't find substantial
>> changes once the bottleneck was hit)
> 
> Nice, I suppose other IO patterns keep the same performance as before.
> 
>> We tuned md with parameters like:
>>
>> echo 4 > /sys/block/md0/md/group_thread_cnt
>> echo 8192 > /sys/block/md0/md/stripe_cache_size
>>
>> For lock contention stats, we just used lockstat[1]; roughly like:
>>
>> echo 1 > /proc/sys/kernel/lock_stat
>> fio test.fio
>> echo 0 > /proc/sys/kernel/lock_stat
>> cat /proc/lock_stat
>>
>> And compared the before and after.
> 
> Thanks for your effort, besides the performance test, please try to run
> mdadm test suites to avoid regression.

Yeah, is there any documentation for that? I tried to look into it but
couldn't figure out how it's run.

I do know that lkp-tests has run it on this series as I did get an error
from it. But while I'm pretty sure that error has been resolved, I was
never able to figure out how to run them locally.

Thanks,

Logan