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

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Message-ID: <20161004191427.GG4205@htj.duckdns.org>
Date:   Tue, 4 Oct 2016 15:14:27 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Paolo Valente <paolo.valente@...more.it>
Cc:     Shaohua Li <shli@...com>, Vivek Goyal <vgoyal@...hat.com>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jens Axboe <axboe@...com>, Kernel-team@...com,
        jmoyer@...hat.com, Mark Brown <broonie@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH V3 00/11] block-throttle: add .high limit

Hello, Paolo.

On Tue, Oct 04, 2016 at 09:02:47PM +0200, Paolo Valente wrote:
> 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.

Hmm... I think we already discussed this but here's a really simple
case.  There are three unknown workloads A, B and C and we want to
give A certain best-effort guarantees (let's say around 80% of the
underlying device) whether A is sharing the device with B or C.

I get that bfq can be a good compromise on most desktop workloads and
behave reasonably well for some server workloads with the slice
expiration mechanism but it really isn't an IO resource partitioning
mechanism.

Thanks.

-- 
tejun