linux-kernel - Re: [PATCH 2/5] vmevent: Convert from deferred timer to deferred work

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Date:	Fri, 08 Jun 2012 03:33:17 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	leonid.moiseichuk@...ia.com
CC:	kosaki.motohiro@...il.com, anton.vorontsov@...aro.org,
	penberg@...nel.org, b.zolnierkie@...sung.com,
	john.stultz@...aro.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org,
	patches@...aro.org, kernel-team@...roid.com
Subject: Re: [PATCH 2/5] vmevent: Convert from deferred timer to deferred
 work

(6/8/12 3:28 AM), leonid.moiseichuk@...ia.com wrote:
>> -----Original Message-----
>> From: ext KOSAKI Motohiro [mailto:kosaki.motohiro@...il.com]
>> Sent: 08 June, 2012 10:23
> ...
>>> If you wakeup only by signal when memory situation changed you can be
>> not mlocked.
>>> Mlocking uses memory very inefficient way and usually cannot be applied
>> for apps which wants to be notified due to resources restrictions.
>>
>> That's your choice. If you don't need to care cache dropping, We don't
>> enforce it. I only pointed out your explanation was technically incorrect.
>
> My explanation is correct. That is an overhead you have to pay if start to
>use API based on polling from user-space and this overhead narrows API
>applicability.
> Moving all times/tracking to kernel avoid useless wakeups in user-space.

Wrong. CPU don't realized the running code belong to userspace or kernel. Every
code just consume a power. That's why polling timer is wrong from point of power
consumption view.

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