Re: [PATCH V3 00/11] block-throttle: add .high limit

[Paolo Valente]

> Il giorno 04 ott 2016, alle ore 20:54, Tejun Heo <tj@xxxxxxxxxx> ha scritto:
> 
> Hello, Paolo.
> 
> On Tue, Oct 04, 2016 at 07:43:48PM +0200, Paolo Valente wrote:
>>> I don't think IO bandwidth does not matter. The problem is bandwidth can't
>>> measure IO cost. For example, you can't say 8k IO costs 2x IO resource than 4k
>>> IO.
>> 
>> For what goal do you need to be able to say this, once you succeeded
>> in guaranteeing bandwidth and low latency to each
>> process/client/group/node/user?
> 
> For resource partitioning mostly.  It's not a single user or purpose
> use case.  The same device gets shared across unrelated workloads and
> we need to guarantee differing levels of quality of service to each
> regardless of the specifics of workload.

That's exactly what BFQ has succeeded in doing in all the tests
devised so far.  Can you give me a concrete example for which I can
try with BFQ and with any other mechanism you deem better.  If
you are right, numbers will just make your point.

Thanks,
Paolo

>  We actually need to be able
> to control IO resources.
> 


> Thanks.
> 
> -- 
> tejun


--
Paolo Valente
Algogroup
Dipartimento di Scienze Fisiche, Informatiche e Matematiche
Via Campi 213/B
41125 Modena - Italy
http://algogroup.unimore.it/people/paolo/