Re: Bloat report 2.6.3 -> 2.6.4

[Matt Mackall]

On Sat, Mar 13, 2004 at 06:08:40PM +0100, Adrian Bunk wrote:
> On Fri, Mar 12, 2004 at 05:53:49PM -0600, Matt Mackall wrote:
> > On Fri, Mar 12, 2004 at 03:22:06PM -0800, Andrew Morton wrote:
> > > Matt Mackall <mpm@xxxxxxxxxxx> wrote:
> > > >
> > > > 2.6.3 -> 2.6.4
> > > > 
> > > >    text	   data	    bss	    dec	    hex	filename
> > > > 3313135	 660247	 162472	4135854	 3f1bae	vmlinux-2.6.3-c2.6.3
> > > > 3342019	 664154	 162344	4168517	 3f9b45	vmlinux-2.6.4-c2.6.3
> > > > 
> > > > [ Results of size <a> <b>. -c2.6.3 means both kernel images were built
> > > > with the 2.6.3 defconfig.
> > > 
> > > But defconfig was changed between 2.6.3 and 2.6.4.
> > 
> > Yes, and I'm attempting to compensate for that because defconfig
> > changes tend to overwhelm other stuff in the results. 
> > 
> > My strategy here doesn't work as well as I'd hoped. I'm taking the
> > defconfig from the previous kernel and then running yes "" | make
> > oldconfig, which sets any new symbols to their defaults. So this deals
> > with case where existing symbols change defaults, but doesn't address
> > new symbols at all.
> > 
> > And what's happening with some of the new symbols is that they're off
> > in defconfig but on in Kconfig. So I need to come up with a way to
> > take the old defconfig and merge in new symbols from the new
> > defconfig. Then throw it at make oldconfig to drop out any obsolete
> > symbols.
> 
> You have to realize that your "automated scheme to measure the growth of 
> the kernel" doesn't work as you might have expected.
> 
> As an example, consider the following option gets added:
> 
>   config ACPI_NEW_OPTION
> 	bool "new option"
> 	depends on ACPI
> 	default y
> 	help
> 	  This option adds support for $new_feature.
> 	  It enlarges your kernel by about 100k.
> 	  It's save to say Y.
> 
> 
> In your size metric, this option would be pure "bloat".

I actually did explicitly note this problem in the part you clipped.
But I think it's fair to say that new features that are on by default
are in fact bloat in some sense.

-- 
Matt Mackall : http://www.selenic.com : Linux development and consulting
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