From 5fb7dc37dc16fbc8b80d81318a582201ef7e280d Mon Sep 17 00:00:00 2001 From: Fenghua Yu Date: Thu, 19 Jul 2007 01:48:12 -0700 Subject: define new percpu interface for shared data per cpu data section contains two types of data. One set which is exclusively accessed by the local cpu and the other set which is per cpu, but also shared by remote cpus. In the current kernel, these two sets are not clearely separated out. This can potentially cause the same data cacheline shared between the two sets of data, which will result in unnecessary bouncing of the cacheline between cpus. One way to fix the problem is to cacheline align the remotely accessed per cpu data, both at the beginning and at the end. Because of the padding at both ends, this will likely cause some memory wastage and also the interface to achieve this is not clean. This patch: Moves the remotely accessed per cpu data (which is currently marked as ____cacheline_aligned_in_smp) into a different section, where all the data elements are cacheline aligned. And as such, this differentiates the local only data and remotely accessed data cleanly. Signed-off-by: Fenghua Yu Acked-by: Suresh Siddha Cc: Rusty Russell Cc: Christoph Lameter Cc: Cc: "Luck, Tony" Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-i386/percpu.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/asm-i386') diff --git a/include/asm-i386/percpu.h b/include/asm-i386/percpu.h index f54830b5d5ac..a7ebd436f3cc 100644 --- a/include/asm-i386/percpu.h +++ b/include/asm-i386/percpu.h @@ -54,6 +54,11 @@ extern unsigned long __per_cpu_offset[]; #define DEFINE_PER_CPU(type, name) \ __attribute__((__section__(".data.percpu"))) __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + __attribute__((__section__(".data.percpu.shared_aligned"))) \ + __typeof__(type) per_cpu__##name \ + ____cacheline_aligned_in_smp + /* We can use this directly for local CPU (faster). */ DECLARE_PER_CPU(unsigned long, this_cpu_off); -- cgit v1.2.2