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

Il giorno 04 ott 2016, alle ore 20:54, Tejun Heo [off-list ref] ha scritto:

Hello, Paolo.

On Tue, Oct 04, 2016 at 07:43:48PM +0200, Paolo Valente wrote:

quoted

quoted

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/