linux-kernel - Re: [PATCH V4 3/4] block: queue work on unbound wq

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Date:	Tue, 9 Apr 2013 15:28:29 +0530
From:	Amit Kucheria <amit.kucheria@...aro.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>,
	Robin Randhawa <robin.randhawa@....com>,
	linux-rt-users@...r.kernel.org,
	Patch Tracking <patches@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Liviu Dudau <Liviu.Dudau@....com>,
	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Steve Bannister <Steve.Bannister@....com>, airlied@...hat.com,
	Arvind Chauhan <arvind.chauhan@....com>, mingo@...hat.com,
	davem@...emloft.net,
	Charles Garcia-Tobin <charles.garcia-tobin@....com>
Subject: Re: [PATCH V4 3/4] block: queue work on unbound wq

On Tue, Apr 9, 2013 at 3:25 PM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 9 April 2013 15:23, Amit Kucheria <amit.kucheria@...aro.org> wrote:
>> On Tue, Apr 9, 2013 at 1:00 PM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
>>> Later one (Power oriented WQ) can be achieved if the workqueue is allocated with
>>
>> Rephrase as "Power-efficient workqueues can be achieved..."
>
> Ok.
>
>>> WQ_UNBOUND flag. To make this compile time configurable with boot time override
>>> this patch adds in another flag WQ_POWER_EFFICIENT. This will be converted to
>>> WQ_UNBOUND (on wq allocation) if CONFIG_WQ_POWER_EFFICIENT is enabled and
>>> bootargs contain workqueue.power_efficient=1. It is unused otherwise and normal
>>> behavior of WQ without this flag is expected.
>>
>> Addition of a new flag seems a bit excessive IMHO. Why can't we just
>> set the UNBOUND flag when the wq_power_efficient module param is set?
>>
>> It would make the patch a lot simpler too.
>
> But how will we know if the user of wq wants to save power or not? He must
> give some flag which is only used when power saving is enabled. We can't
> set WQ_UNBOUND for all wqs.

You have the Kconfig option + the module param for that. You don't need a flag.
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