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

[Zhi Yong Wu]

On Mon, Oct 17, 2011 at 11:54 PM, Stefan Hajnoczi <address@hidden> wrote:
> On Mon, Oct 17, 2011 at 11:26 AM, Kevin Wolf <address@hidden> wrote:
>> Am 26.09.2011 09:24, schrieb Zhi Yong Wu:
>>> On Sat, Sep 24, 2011 at 12:19 AM, Kevin Wolf <address@hidden> wrote:
>>>> Am 08.09.2011 12:11, schrieb Zhi Yong Wu:
>>>>> 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.
>>>>>      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.
>>>>>
>>>>> For these problems, if you have nice thought, pls let us know.:)
>>>>>
>>>>> Signed-off-by: Zhi Yong Wu <address@hidden>
>>>>> ---
>>>>>  block.c |  259 
>>>>> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
>>>>>  block.h |    1 -
>>>>>  2 files changed, 248 insertions(+), 12 deletions(-)
>>>>
>>>> One general comment: What about synchronous and/or coroutine I/O
>>>> operations? Do you think they are just not important enough to consider
>>>> here or were they forgotten?
>>> For sync ops, we assume that it will be converse into async mode at
>>> some point of future, right?
>>> For coroutine I/O, it is introduced in image driver layer, and behind
>>> bdrv_aio_readv/writev. I think that we need not consider them, right?
>>
>> Meanwhile the block layer has been changed to handle all requests in
>> terms of coroutines. So you would best move your intercepting code into
>> the coroutine functions.
>
> Some additional info: the advantage of handling all requests in
> coroutines is that there is now a single place where you can put I/O
> throttling.  It will work for bdrv_read(), bdrv_co_readv(), and
> bdrv_aio_readv().  There is no code duplication, just put the I/O
> throttling logic in bdrv_co_do_readv().
got it. thanks.
>
> Stefan
>



-- 
Regards,

Zhi Yong Wu