Re: [PATCH v8 3/4] block: add block timer and throttling algorithm

[Zhi Yong Wu <zwu.kernel@gmail.com>]

On Wed, Sep 14, 2011 at 6:50 PM, Marcelo Tosatti <mtosatti@redhat.com> wrote:
> On Tue, Sep 13, 2011 at 11:09:46AM +0800, Zhi Yong Wu wrote:
>> On Fri, Sep 9, 2011 at 10:44 PM, Marcelo Tosatti <mtosatti@redhat.com> wrote:
>> > On Thu, Sep 08, 2011 at 06:11:07PM +0800, Zhi Yong Wu wrote:
>> >> Note:
>> >>      1.) When bps/iops limits are specified to a small value such as 511 bytes/s, this VM will hang up. We are considering how to handle this senario.
>> >
>> > You can increase the length of the slice, if the request is larger than
>> > slice_time * bps_limit.
>> Yeah, but it is a challenge for how to increase it. Do you have some nice idea?
>
> If the queue is empty, and the request being processed does not fit the
> queue, increase the slice so that the request fits.
Sorry for late reply. actually, do you think that this scenario is
meaningful for the user?
Since we implement this, if the user limits the bps below 512
bytes/second, the VM can also not run every task.
Can you let us know why we need to make such effort?

>
> That is, make BLOCK_IO_SLICE_TIME dynamic and adjust it as described
> above (if the bps or io limits change, reset it to the default
> BLOCK_IO_SLICE_TIME).
>
>> >>      2.) When "dd" command is issued in guest, if its option bs is set to a large value such as "bs=1024K", the result speed will slightly bigger than the limits.
>> >
>> > Why?
>> This issue has not existed. I will remove it.
>> When drive bps=1000000, i did some testings on guest VM.
>> 1.) bs=1024K
>> 18+0 records in
>> 18+0 records out
>> 18874368 bytes (19 MB) copied, 26.6268 s, 709 kB/s
>> 2.) bs=2048K
>> 18+0 records in
>> 18+0 records out
>> 37748736 bytes (38 MB) copied, 46.5336 s, 811 kB/s
>>
>> >
>> > There is lots of debugging leftovers in the patch.
>> sorry, i forgot to remove them.
>> >
>> >
>
>



-- 
Regards,

Zhi Yong Wu