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From: Paolo Valente <paolo.valente@linaro.org>
To: Tejun Heo <tj@kernel.org>
Cc: "Michal Koutný" <mkoutny@suse.com>,
	"Jens Axboe" <axboe@kernel.dk>,
	linux-block <linux-block@vger.kernel.org>,
	"Jan Kara" <jack@suse.cz>,
	cgroups@vger.kernel.org
Subject: Re: BFQ cgroup weights range
Date: Fri, 27 Aug 2021 10:33:01 +0200	[thread overview]
Message-ID: <72DB38C2-196C-4F55-B1A1-B8EA55667057@linaro.org> (raw)
In-Reply-To: <YSfOhM9+uJ5/FzY2@mtj.duckdns.org>



> Il giorno 26 ago 2021, alle ore 19:25, Tejun Heo <tj@kernel.org> ha scritto:
> 
> On Thu, Aug 26, 2021 at 03:12:12PM +0200, Michal Koutný wrote:
>> On Tue, Aug 24, 2021 at 02:51:47PM +0200, Paolo Valente <paolo.valente@linaro.org> wrote:
>>> BFQ inherited these constants when we forked it from CFQ.  I'm ok with
>>> increasing max weight to 10000.  I only wonder whether this would
>>> break some configuration, as the currently maximum weight would not be
>>> the maximum weight any longer.
>> 
>> Thanks for the reply. Let me form the idea as a patch (and commit
>> message) and discuss based on that if needed (+ccrosspost into cgroups
>> ML).
>> 
>> -- >8 --
>> From: Michal Koutný <mkoutny@suse.com>
>> Subject: [PATCH] block, bfq: Accept symmetric weight adjustments
>> 
>> The allowed range for BFQ weights is currently 1..1000 with 100 being
>> the default. There is no apparent reason to not accept weight
>> adjustments of same ratio on both sides of the default. This change
>> makes the attribute domain consistent with other cgroup (v2) knobs with
>> the weight semantics.
>> 
>> This extension of the range does not restrict existing configurations
>> (quite the opposite). This may affect setups where weights >1000 were
>> attempted to be set but failed with the default 100. Such cgroups would
>> attain their intended weight now. This is a changed behavior but it
>> rectifies the situation (similar intention to the commit 69d7fde5909b
>> ("blkcg: use CGROUP_WEIGHT_* scale for io.weight on the unified
>> hierarchy") for CFQ formerly (and v2 only)).
>> 
>> Additionally, the changed range does not imply all IO workloads can be
>> really controlled to achieve the widest possible ratio 1:10^4.
>> 
>> Signed-off-by: Michal Koutný <mkoutny@suse.com>
> 
> Looks fine to me.
> 
> Acked-by: Tejun Heo <tj@kernel.org>
> 

Acked-by: Paolo Valente <paolo.valente@linaro.org>

Thanks for this improvement,
Paolo

> Thanks.
> 
> -- 
> tejun


      reply	other threads:[~2021-08-27  8:33 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-24 10:56 BFQ cgroup weights range Michal Koutný
2021-08-24 12:51 ` Paolo Valente
2021-08-26 13:12   ` Michal Koutný
2021-08-26 17:25     ` Tejun Heo
2021-08-27  8:33       ` Paolo Valente [this message]

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