Messages in this thread Patch in this message | | | Date | Thu, 21 Jun 2007 21:56:59 +0200 | From | Ingo Molnar <> | Subject | Re: [BUG] long freezes on thinkpad t60 |
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:
> Umm. i386 spinlocks could and should be *one*byte*. > > In fact, I don't even know why they are wasting four bytes right now: > the fact that somebody made them an "int" just wastes memory. All the > actual code uses "decb", so it's not even a question of safety. I > wonder why we have that 32-bit thing and the ugly casts. > > Ingo, any memory of that?
no real reason that i can recall - i guess nobody dared to touch it because it used to have that 'volatile', indicating black voodoo ;-) Now that the bad stigma has been removed, we could try the patch below. It boots fine here, and we save 1K of kernel text size:
text data bss dec hex filename 6236003 611992 401408 7249403 6e9dfb vmlinux.before 6235075 611992 401408 7248475 6e9a5b vmlinux.after
I can understand why no data is saved by this change: gcc is aligning the next field to a natural boundary anyway and we dont really have arrays of spinlocks (fortunately). [and we save no data even if using the ((packed)) attribute.] Perhaps some data structure that is never in the kernel image itself still got smaller? Any good way to determine that?
But why is the text size different? Ah: i think it's spin_lock_init() getting shorter :-)
but this is certainly not something for 2.6.22, it's an early 2.6.23 matter i suspect.
Ingo
-------------------> From: Ingo Molnar <mingo@elte.hu> Subject: [patch] spinlocks i386: change them to byte fields
all spinlock ops are on byte operands, so change the spinlock field to be unsigned char. This saves a bit of kernel text size:
text data bss dec hex filename 6236003 611992 401408 7249403 6e9dfb vmlinux.before 6235075 611992 401408 7248475 6e9a5b vmlinux.after
Signed-off-by: Ingo Molnar <mingo@elte.hu> --- include/asm-i386/spinlock_types.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
Index: linux/include/asm-i386/spinlock_types.h =================================================================== --- linux.orig/include/asm-i386/spinlock_types.h +++ linux/include/asm-i386/spinlock_types.h @@ -6,7 +6,7 @@ #endif typedef struct { - unsigned int slock; + unsigned char slock; } raw_spinlock_t; #define __RAW_SPIN_LOCK_UNLOCKED { 1 } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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