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authorOlof Johansson <olof@austin.ibm.com>2005-04-16 15:24:38 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:24:38 -0700
commite63f8f439de010b6227c0c9c6f56e2c44dbe5dae (patch)
treeeb80efbfb8e4c55a94610d30fb8424cd128ffe8b /include
parent89e09f5ebba4bcde9852e4be4af536d5b691f20a (diff)
[PATCH] ppc64: no prefetch for NULL pointers
For prefetches of NULL (as when walking a short linked list), PPC64 will in some cases take a performance hit. The hardware needs to do the TLB walk, and said walk will always miss, which means (up to) two L2 misses as penalty. This seems to hurt overall performance, so for NULL pointers skip the prefetch alltogether. Signed-off-by: Olof Johansson <olof@austin.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include')
-rw-r--r--include/asm-ppc64/processor.h6
1 files changed, 6 insertions, 0 deletions
diff --git a/include/asm-ppc64/processor.h b/include/asm-ppc64/processor.h
index eb33d33cfd6..cae65b30adb 100644
--- a/include/asm-ppc64/processor.h
+++ b/include/asm-ppc64/processor.h
@@ -642,11 +642,17 @@ static inline unsigned long __pack_fe01(unsigned int fpmode)
static inline void prefetch(const void *x)
{
+ if (unlikely(!x))
+ return;
+
__asm__ __volatile__ ("dcbt 0,%0" : : "r" (x));
}
static inline void prefetchw(const void *x)
{
+ if (unlikely(!x))
+ return;
+
__asm__ __volatile__ ("dcbtst 0,%0" : : "r" (x));
}