[dm-devel] Re: Too many I/O controller patches

[Andrea Righi <righi andrea gmail com>]

Satoshi UCHIDA wrote:
>  Andrea's requirement is
>    * to be able to set and control by absolute(direct) performance.

     * improve IO performance predictability of each cgroup
       (try to guarantee more precise IO performance values)

> And, he gave a advice "Can't a framework which organized each way,
> such as I/O elevator, be made?".
> I try to consider such framework (in elevator layer or block layer).

It would be probably the best place to evaluate the "cost" of each
IO operation.

> I think that OOM problems caused by memory/cache systems.
> So, it will be better that I/O controller created out of these problems
> first, although a lateness of the I/O device would be related.
> If these problem can be resolved, its technique should be applied into 
> normal I/O control as well as cgroups.
> 
> Buffered write I/O is also related with cache system.
> We must consider this problem as I/O control.

Agree. At least, maybe we should consider if an IO controller could be
a valid solution also for these problems.

>> I did some experiments trying to implement minimum bandwidth requirements
>> for my io-throttle controller, mapping the requirements to CFQ prio and
>> using the Satoshi's controller. But this needs additional work and
>> testing right now, so I've not posted anything yet, just informed
>> Satoshi about this.
> 
> I'm very interested in this results.

I'll collect some numbers and keep you informed.

-Andrea