linux-kernel - Re: [PATCH v2 00/12] Improve Raid5 Lock Contention

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Message-ID: <CALTww28SuvhzCL6p4L9y9ZH5Mmgss-tTm_QzbEo60hZOXAUS0A@mail.gmail.com>
Date:   Tue, 26 Apr 2022 00:12:09 +0800
From:   Xiao Ni <xni@...hat.com>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     Guoqing Jiang <guoqing.jiang@...ux.dev>,
        open list <linux-kernel@...r.kernel.org>,
        linux-raid <linux-raid@...r.kernel.org>,
        Song Liu <song@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Stephen Bates <sbates@...thlin.com>,
        Martin Oliveira <Martin.Oliveira@...eticom.com>,
        David Sloan <David.Sloan@...eticom.com>
Subject: Re: [PATCH v2 00/12] Improve Raid5 Lock Contention

On Mon, Apr 25, 2022 at 11:39 PM Logan Gunthorpe <logang@...tatee.com> wrote:
>
>
>
> 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.
>

Hi Logan

You can clone the mdadm repo at
git://git.kernel.org/pub/scm/utils/mdadm/mdadm.git
Then you can find there is a script test under the directory. It's not
under the tests directory.
The test cases are under tests directory.

Regards
Xiao