Re: [PATCH v2 00/12] Improve Raid5 Lock Contention
From: Xiao Ni
Date: Mon Apr 25 2022 - 12:12:36 EST
On Mon, Apr 25, 2022 at 11:39 PM Logan Gunthorpe <logang@xxxxxxxxxxxx> 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; 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.
You can clone the mdadm repo at
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.