Re: Re: [patch]raid5: fix directio regression

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

On 2012-08-07 13:32 Shaohua Li <shli@kernel.org> Wrote:
>2012/8/7 Jianpeng Ma <majianpeng@gmail.com>:
>> On 2012-08-07 11:22 Shaohua Li <shli@kernel.org> Wrote:
>>>My directIO randomwrite 4k workload shows a 10~20% regression caused by commit
>>>895e3c5c58a80bb. directIO usually is random IO and if request size isn't big
>>>(which is the common case), delay handling of the stripe hasn't any advantages.
>>>For big size request, delay can still reduce IO.
>>>
>>>Signed-off-by: Shaohua Li <shli@fusionio.com>
[snip]
>>>--
>> May be used size to judge is not a good method.
>> I firstly sended this patch, only want to control direct-write-block,not for reqular file.
>> Because i think if someone used direct-write-block for raid5,he should know the feature of raid5 and he can control
>> for write to full-write.
>> But at that time, i did know how to differentiate between regular file and block-device.
>> I thik we should do something to do this.
>
>I don't think it's possible user can control his write to be a
>full-write even for
>raw disk IO. Why regular file and block device io matters here?
>
>Thanks,
>Shaohua
Another problem is the size. How to judge the size is large or not?
A syscall write is a dio and a dio may be split more bios.
For my workload, i usualy write chunk-size.
But your patch is judge by bio-size.