linux-kernel - Re: [PATCH 08/10] blkcg: implement blk-iocost

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]

Message-Id: <A69EF8D0-8156-46DB-A4DA-C5334764116E@linaro.org>
Date:   Wed, 11 Sep 2019 10:18:53 +0200
From:   Paolo Valente <paolo.valente@...aro.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     Michal Koutný <mkoutny@...e.com>,
        Johannes Weiner <hannes@...xchg.org>, clm@...com,
        dennisz@...com, newella@...com, Li Zefan <lizefan@...wei.com>,
        Jens Axboe <axboe@...nel.dk>,
        Josef Bacik <josef@...icpanda.com>,
        Josef Bacik <jbacik@...com>, kernel-team@...com,
        Rik van Riel <riel@...riel.com>, cgroups@...r.kernel.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/10] blkcg: implement blk-iocost



> Il giorno 10 set 2019, alle ore 18:08, Tejun Heo <tj@...nel.org> ha scritto:
> 
> Hello, Michal.
> 
> On Tue, Sep 10, 2019 at 02:55:14PM +0200, Michal Koutný wrote:
>> This adds the generic io.weight attribute. How will this compose with
>> the weight from IO schedulers? (AFAIK, only BFQ allows proportional
>> control as of now. +CC Paolo.)
> 
> The two being enabled at the same time doesn't make sense, so we can
> just switch over to bfq when bfq is selected as the iosched.  I asked
> what Paolo wanted to do in terms of interface a couple times now but
> didn't get an answer and he posted a patch which makes the two
> controllers conflict, so....  Paolo, so it looks like you want to
> rename all bfq files to drop the bfq prefix, right?

Yep, mainly because ... this is the solution you voted and you
yourself proposed [1] :)

[1] https://patchwork.kernel.org/patch/10988261/

>  I can implement
> the switching if so.
> 

That would be perfect.

Thanks,
Paolo

>> I see this attributes are effectively per-cgroup per-device. Apparently,
>> one device should have only one weight across hierarchy. Would it make
>> sense to have io.bfq.weight and io.cost.weight with disjunctive devices?
> 
> It never makes sense to have both enabled, so I don't think that
> interface makes sense.
> 
>>> +		.name = "cost.qos",
>>> +		.flags = CFTYPE_ONLY_ON_ROOT,
>>> [...]
>>> +		.name = "cost.model",
>>> +		.flags = CFTYPE_ONLY_ON_ROOT,
>> I'm concerned that these aren't true cgroup attributes. The root cgroup
>> would act as container for global configuration options. Wouldn't these
>> values better fit as (configurable) attributes of the respective
>> devices?
> 
> Initially, I put them under block device sysfs but it was too clumsy
> with different config file formats and all.  I think it's better to
> have global controller configs at the root cgroup.
> 
>> Secondly, how is CFTYPE_ONLY_ON_ROOT supposed to be presented in cgroup
>> namespaces?
> 
> Not at all.  These are system-wide configs.  cgroup namespaces
> shouldn't have anything which aren't in non-root cgroups.
> 
> Thanks.
> 
> -- 
> tejun