Re: [PATCH] cgroup: limit block I/O bandwidth

[Andrea Righi]

Balbir Singh wrote:
> * Andrea Righi <righiandr@xxxxxxxxxxxxxxxxxxxxx> [2008-01-23 16:23:59]:
> 
>> Probably tracking who dirtied the pages would be the best approach, but
>> we want also to reduce the overhead of this tracking. So, we should find
>> a smart way to track which cgroup dirtied the pages and then only when
>> the i/o scheduler dispatches the write requests of those pages, account
>> the i/o operations to the opportune cgroup. In this way throttling could
>> be done probably in __set_page_dirty() as well.
>>
> 
> I think the OpenVZ controller works that way.

Well... looking at the code it seems that OpenVZ doesn't use this
strategy, instead performs UBC-based I/O accounting looking at the
__set_page_dirty*() for writes and submit_bio() for reads. Then,
independently from accounting data, it uses per-UBC i/o priority model
that is mapped directly on the CFQ i/o priority model.

-Andrea
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