linux-kernel - Re: [Bug #11342] Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c

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Message-ID: <48B4AE68.4040205@snapgear.com>
Date:	Wed, 27 Aug 2008 11:31:20 +1000
From:	Greg Ungerer <gerg@...pgear.com>
To:	Parag Warudkar <parag.lkml@...il.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Adrian Bunk <bunk@...sta.de>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"Alan D. Brunelle" <Alan.Brunelle@...com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Ingo Molnar <mingo@...e.hu>, linux-embedded@...r.kernel.org
Subject: Re: [Bug #11342] Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c - bisected


Parag Warudkar wrote:
> On Tue, Aug 26, 2008 at 8:53 PM, Greg Ungerer <gerg@...pgear.com> wrote:
> 
>> I have some simple devices (network access/routers) with 8MB of RAM,
>> at power up not really being configured to do anything running 25
>> processes. (Heck there is over 10 kernel processes running!). Configure
>> some interfaces and services and that will easily push past 40.
>> I'd be happy with a 160k saving :-)
>>
> 
> So you really need to run all 25 processes on that 8Mb box?

Yes, of course. Considerable effort has been put into running
a minimal set of processes (that still for fills the required function
set of this device).


> (For reference even the NGW100 development board comes with 16Mb RAM).

Lots of development boards are fitted with lots of RAM.

And the pressure will still be on in _real_ products to reduce
the RAM footprint as much as possible. There are exceptions but
generally less is cheaper. Simple economics really.


> Even if you do need those all 25 processes on the 8Mb box, fixing the
> memory usage of those user space hogs is lot better than trying to
> save 160Kb in kernel stacks.

Yep, been done too. You don't squeeze a lot into these smaller
devices without looking at everything in it.


> Last I looked, user space wasn't particularly frugal with memory usage.

Then you haven't looked in the right places :-)

There are plenty of choices for making things small in user space.
Simple stuff like using uClibc, busybox, etc.

In this specific example things like /bin/init is 10k, /bin/inetd
is 10k, /bin/crond is 11k, etc. (Ofcourse it is a shared uClibc setup,
uClibc is ~300k). And XIP can help out here too.

Regards
Greg



------------------------------------------------------------------------
Greg Ungerer  --  Chief Software Dude       EMAIL:     gerg@...pgear.com
Secure Computing Corporation                PHONE:       +61 7 3435 2888
825 Stanley St,                             FAX:         +61 7 3891 3630
Woolloongabba, QLD, 4102, Australia         WEB: http://www.SnapGear.com
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