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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 4 Oct 2016 12:27:59 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Paolo Valente <paolo.valente@...more.it>
Cc:     Vivek Goyal <vgoyal@...hat.com>, Shaohua Li <shli@...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,

On Tue, Oct 04, 2016 at 06:22:28PM +0200, Paolo Valente wrote:
> Could you please elaborate more on this point?  BFQ uses sectors
> served to measure service, and, on the all the fast devices on which
> we have tested it, it accurately distributes
> bandwidth as desired, redistributes excess bandwidth with any issue,
> and guarantees high responsiveness and low latency at application and
> system level (e.g., ~0 drop rate in video playback, with any background
> workload tested).

The same argument as before.  Bandwidth is a very bad measure of IO
resources spent.  For specific use cases (like desktop or whatever),
this can work but not generally.

> Could you please suggest me some test to show how sector-based
> guarantees fails?

Well, mix 4k random and sequential workloads and try to distribute the
acteual IO resources.

Thanks.

-- 
tejun