On Thu, 22 Dec 2011 15:53:49 +0000
"Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> Due to the alignment of following variables, these typically consume
> more than just the single byte that 'bool' requires, and as there are
> a few hundred instances, the cache pollution (not so much the waste of
> memory) sums op. Put these variables into their own section, outside
> of half way frequently used memory range.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> ---
> include/asm-generic/bug.h | 6 +++---
> include/asm-generic/vmlinux.lds.h | 1 +
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
> --- 3.2-rc6/include/asm-generic/bug.h
> +++ 3.2-rc6-warn-once-flag-cold/include/asm-generic/bug.h
> @@ -134,7 +134,7 @@ extern void warn_slowpath_null(const cha
> #endif
>
> #define WARN_ON_ONCE(condition) ({ \
> - static bool __warned; \
> + static bool __section(.data.unlikely) __warned; \
> int __ret_warn_once = !!(condition); \
> \
> if (unlikely(__ret_warn_once)) \
> @@ -144,7 +144,7 @@ extern void warn_slowpath_null(const cha
> })
>
> #define WARN_ONCE(condition, format...) ({ \
> - static bool __warned; \
> + static bool __section(.data.unlikely) __warned; \
> int __ret_warn_once = !!(condition); \
> \
> if (unlikely(__ret_warn_once)) \
> @@ -154,7 +154,7 @@ extern void warn_slowpath_null(const cha
> })
>
> #define WARN_TAINT_ONCE(condition, taint, format...) ({ \
> - static bool __warned; \
> + static bool __section(.data.unlikely) __warned; \
> int __ret_warn_once = !!(condition); \
> \
> if (unlikely(__ret_warn_once)) \
> --- 3.2-rc6/include/asm-generic/vmlinux.lds.h
> +++ 3.2-rc6-warn-once-flag-cold/include/asm-generic/vmlinux.lds.h
> @@ -167,6 +167,7 @@
> CPU_KEEP(exit.data) \
> MEM_KEEP(init.data) \
> MEM_KEEP(exit.data) \
> + *(.data.unlikely) \
> STRUCT_ALIGN(); \
> *(__tracepoints) \
> /* implement dynamic printk debug */ \
The patch seems reasonable.
printk_once() should also be converted. And ata_print_version_once(),
if it insists on continuing to exist. Also rcu_lockdep_assert().
My MUA (sylpheed) is unable to generate a plain-text version of the
patch for me, so much hand-editing will be needed. It would be nice
if the patch could be demangled at the sending end, please.
I agree that linux-kernel should have been cc'ed on a change of this
nature.
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