Re: RFC: remove __read_mostly

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Matt Mackall a écrit :
On Thu, Dec 13, 2007 at 11:20:44PM +0100, Adrian Bunk wrote:
I tried the following patch with a full x86 .config [1]:

--- a/include/asm-x86/cache.h
+++ b/include/asm-x86/cache.h
-#define __read_mostly __attribute__((__section__(".data.read_mostly")))
+/* #define __read_mostly __attribute__((__section__(".data.read_mostly"))) */

The result [2,3] was:

-rwxrwxr-x 1 bunk bunk 46607243 2007-12-13 19:50 vmlinux.old
-rwxrwxr-x 1 bunk bunk 46598691 2007-12-13 21:55 vmlinux

It's not a surprise that the kernel can become bigger when __read_mostly gets used, especially in cases where __read_mostly prevents gcc optimizations.

My question is:
Is there anywhere in the kernel a case where __read_mostly brings a measurable improvement or can it be removed?

Yes, but perhaps we can put it under CONFIG_BASE_FULL?

Yes, we probably can do something like that (in addition to !CONFIG_SMP)





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