linux-kernel - Re: [PATCH] Remove CONFIG_PM altogether, enable power management all the time

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Date:	Wed, 9 Feb 2011 03:41:44 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Tim Bird <tbird20d@...il.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Len Brown <len.brown@...el.com>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-embedded@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] Remove CONFIG_PM altogether, enable power management all
 the time


* Tim Bird <tbird20d@...il.com> wrote:

> On Tue, Feb 8, 2011 at 4:21 AM, Ingo Molnar <mingo@...e.hu> wrote:
>
> > Rafael, could you do a defconfig-ish x86 build with and without CONFIG_PM, and 
> > post the 'size vmlinux' comparison - so that we can see the size difference? We 
> > make some things CONFIG_EXPERT configurable just to enable folks who *really* 
> > want to cut down on kernel size to configure it out.
> 
> I'm one of those people who *really* wants to cut down the kernel size. I've 
> recently worked on a product where the kernel RAM budget is ~1M.

Did that kernel have CONFIG_PM disabled?

> > Note that those usecases, even if they want a super-small kernel, might not care 
> > about PM at all while they care about size: small boot kernels in ROMs, or 
> > simple devices where CPU-idling implies deep low power mode, etc.
>
> So the vmlinux size comparisons would be needed really. If it's 5k nobody will 
> care. I care about 5K.  (But honestly, I don't actively hunt stuff less than 10K 
> in size, because there's too many of them to chase, currently).

The numbers that Frank Rowand sent show 40K+:

|
| For 2.6.38-rc4, x86_64, CONFIG_NR_CPUS=4:
|
| size vmlinux
|    text     data       bss       dec      hex  filename
|
| 6553910  3555020   9994240  20103170  132c002  vmlinux    with    CONFIG_PM
| 6512652  3553116   9994240  20060008  1321768  vmlinux    without CONFIG_PM
|
|   41258     1904         0     43162                      delta
|

Thanks,

	Ingo
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