linux-kernel - Re: [PATCH 0/3] ARM 4Kstacks: introduction

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Message-ID: <yw1x1uu5p3sc.fsf@unicorn.mansr.com>
Date:	Sat, 22 Oct 2011 14:13:55 +0100
From:	Måns Rullgård <mans@...sr.com>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	linux-arm-kernel@...ts.infradead.org,
	Tim Bird <tim.bird@...sony.com>, Joe Perches <joe@...ches.com>,
	linux kernel <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Russell King <rmk@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 0/3] ARM 4Kstacks: introduction

Ming Lei <tom.leiming@...il.com> writes:

> On Wed, Oct 19, 2011 at 6:51 PM, Arnd Bergmann <arnd@...db.de> wrote:
>> On Tuesday 18 October 2011 17:26:44 Tim Bird wrote:
>>> Even inside Sony, usage of 4K stacks is limited
>>> to some very special cases, where memory is exceedingly
>>> tight (we have one system with 4M of RAM).  And we
>>> don't mind lopping off features or coding around
>>> problem areas to support our special case.
>>
>> I would imagine that in those cases, you can gain more by reducing the
>> number of threads in the system. What is the highest number of
>> concurrent threads that you expect in a limited use case with no
>> networking or block devices?
>
> If system run for some time, sometimes it may be difficult for
> memory allocator to allocate 2 continuous page frames even  there are
> many spare page frames in system because of
> fragment issue, so the patch does make sense. Anyway,
> it provides one option for user to apply 4k stack to avoid
> such kind of process creation failure.

Can't page migration be used in these situations?

-- 
Måns Rullgård
mans@...sr.com
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