Re: [PATCH] sched: Move cpu masks from kernel/sched.c into kernel/cpu.c

Max Krasnyansky
2008-05-30T04:16:32Z

Paul Jackson wrote:
> Max wrote:
>> kernel/cpu.c is now built for the UP kernel too, but it does not
>> affect the size the kernel sections.
>
> I don't think this is possible. It must affect the size.
>
> The patch moves kernel/cpu.o from being included only if CONFIG_SMP,
> to being included always:
>
> obj-y = sched.o fork.o exec_domain.o panic.o printk.o profile.o \
> - exit.o itimer.o time.o softirq.o resource.o \
> + cpu.o exit.o itimer.o time.o softirq.o resource.o \
> sysctl.o capability.o ptrace.o timer.o user.o \
> signal.o sys.o kmod.o workqueue.o pid.o \
> rcupdate.o extable.o params.o posix-timers.o \
> @@ -27,7 +27,7 @@ obj-$(CONFIG_RT_MUTEXES) += rtmutex.o
> obj-$(CONFIG_DEBUG_RT_MUTEXES) += rtmutex-debug.o
> obj-$(CONFIG_RT_MUTEX_TESTER) += rtmutex-tester.o
> obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
> -obj-$(CONFIG_SMP) += cpu.o spinlock.o
> +obj-$(CONFIG_SMP) += spinlock.o
>
> The kernel/cpu.o object file is non-empty; it has size,
> perhaps 1 or 2 kbytes of text, and a little bit of data.
>
> So adding it to builds which disabled SMP must add to the
> size of the resultant kernel, by my thinking anyway.

All the code is ifdefed under CONFIG_SMP. So there is no code in the !SMP
case, just three masks. When you mentioned it first time I went back and
rebuilt the !SMP kernel with and without the patch. Luckily I have a
ridiculously fast 8way box here so I went ahead and verified it again.

Before:
size vmlinux
text data bss dec hex filename
3305622 306420 310352 3922393 3bd9d9 vmlinux

size kernel/cpu.o
size: 'kernel/cpu.o': No such file

After:
size vmlinux
text data bss dec hex filename
3305621 306420 310352 3922393 3bd9d9 vmlinux

size kernel/cpu.o
text data bss dec hex filename
96 24 0 120 78 kernel/cpu.o

Max