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SubjectRe: [RFC] block/throttle: Add IO throttled information in blkcg.
Hi Vivek,
On 05/22/2012 07:11 PM, Vivek Goyal wrote:
> On Tue, May 22, 2012 at 04:10:36PM +0800, Tao Ma wrote:
>> From: Tao Ma <boyu.mt@taobao.com>
>>
>> Currently, if the IO is throttled by io-throttle, the SA has no idea of
>> the situation and can't report it to the real application user about
>> that he/she has to do something. So this patch adds a new interface
>> named blkio.throttle.io_throttled which indicates how many IOs are
>> currently throttled.
>
> If the only purpose is to know whether IOs are being throttled, why
> not just scan for the rules and see if respective device has any
> throttling rules or not.
>
> Even if you introduce this interface, you will end up scanning for
> throttled ios against that particular device. And if IO is not happening
> at that moment or if IO rate is not exceeding the rate limit, there
> might not be any throttled ios and one might get misled.
>
> So for your purpose a better interface sounds like scanning for throttling
> rules instead of this new interface.
>
>>
>> I am not sure whether it is OK to add this information to the generic
>> blkcg since it is only io-throttle related, but I don't find a way to
>> only store it into the blkcg io-throttle. And that's the reason this
>> is only a RFC. Any suggestions? Thanks.
>
> Tejun has changed the code in this area and new code will allow you to
> introduce this file in blk-throttle.c. All that code is sitting in Jens's
> block tree.
I am just trying to rebase my patch according to your suggestion, but I
can't find the change you mentioned above. So could you please tell me
where I can find the related change so that I can base my work on?

Thanks
Tao
>
> Thanks
> Vivek
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