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SubjectRe: [pull request] getting rid of __cpuinit
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On Saturday, 25 of October 2008, Arjan van de Ven wrote:
> On Sat, 25 Oct 2008 18:21:16 +0200
> Sam Ravnborg <sam@ravnborg.org> wrote:
>
> > On Sat, Oct 25, 2008 at 08:06:38AM -0700, Arjan van de Ven wrote:
> > > On Sat, 25 Oct 2008 16:35:28 +0200
> > > Sam Ravnborg <sam@ravnborg.org> wrote:
> > > > So if you look at the size of the cpuinit/exit sections in the
> > > > before case you get the real space saving that is lost in the
> > > > embedded case after your patch is applied.
> > > > The space savings that happen after early init.
> > >
> > > [linux.trees.git]# objdump -h vmlinux.before | grep init.text
> > > 25 .init.text 00037c25 ffffffff8152a000 000000000152a000
> > > 0092a000 [inux.trees.git]# objdump -h vmlinux.after | grep
> > > init.text 25 .init.text 000316c2 ffffffff81542000
> > > 0000000001542000 00942000
> >
> > So with your config we will loose a saving of 25955 bytes
> > of text.
> >
> > I tried to look a the numbers of a defconfig build here.
> > cpuinit.text equals 0x5d97 = 23959
> > cpuinit.data equals 0x3574 = 13684
> >
> > [objdump of vmlinux.o gives you the size of the cpuinit sections]
> >
> > So if we decide to drop cpuinit then it should be based on the
> > above figure and not the 2k figure you gave in the original mail.
> >
> > Or even better we should see the difference with a typical
> > embedded configuration and not some big defconfig build.
> > I will assume the saving is less on a typical embedded
> > configuration.
>
> it will be; on x86 you end up inheriting all cpu vendors init code.
> on embedded you only have the dedicated CPU code.
>
> ... just that on x86... nobody seems to be in this position, it's
> almost impossble to have HOTPLUG_CPU even be asked.

FWIW, I like the idea of removing __cpuinit. It often is quite difficult to
determine if given piece of code should be marked as __cpuinit and that leads
to bugs that are not so easy to resolve.

Thanks,
Rafael



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