Re: Re: [patch 2/2 v3]raid5: create multiple threads to handle stripes

["Jianpeng Ma" <majianpeng@gmail.com>]

On 2012-08-13 08:21 Shaohua Li <shli@kernel.org> Wrote:
>2012/8/11 Jianpeng Ma <majianpeng@gmail.com>:
>> On 2012-08-09 16:58 Shaohua Li <shli@kernel.org> Wrote:
>>>This is a new tempt to make raid5 handle stripes in multiple threads, as
>>>suggested by Neil to have maxium flexibility and better numa binding. It
[snip]
>> 2: Test 'dd if=/dev/zero of=/dev/md0 bs=2M ', the performance regress remarkable.
>> auxthread_number=0, 200MB/s;
>> auxthread_number=4, 95MB/s.
>
>So multiple threads handle stripes reduce request merge. In your
>workload, raid5d isn't a bottleneck at all. In practice, I thought only
>array which can drive high IOPS needs enable multi thread. And
>if you create multiple threads, better let the threads handle different
>cpus.
If dd write using buffer-mode, the make-rquest is exec by kernel-thread "flush-n:0".
So we only used multiple thread to write by odirect or sync to achieve the result which we wanted.
>
>Thanks,
>Shaohua