aboutsummaryrefslogtreecommitdiff
path: root/include/linux
diff options
context:
space:
mode:
authorIngo Molnar <mingo@elte.hu>2009-03-02 11:00:57 +0100
committerIngo Molnar <mingo@elte.hu>2009-03-02 11:06:49 +0100
commitf180053694b43d5714bf56cb95499a3c32ff155c (patch)
tree00286fcc88d2842629b039da4009a1332b3a1719 /include/linux
parent34754b69a6f87aa6aa2860525a82f12532f83afd (diff)
x86, mm: dont use non-temporal stores in pagecache accesses
Impact: standardize IO on cached ops On modern CPUs it is almost always a bad idea to use non-temporal stores, as the regression in this commit has shown it: 30d697f: x86: fix performance regression in write() syscall The kernel simply has no good information about whether using non-temporal stores is a good idea or not - and trying to add heuristics only increases complexity and inserts fragility. The regression on cached write()s took very long to be found - over two years. So dont take any chances and let the hardware decide how it makes use of its caches. The only exception is drivers/gpu/drm/i915/i915_gem.c: there were we are absolutely sure that another entity (the GPU) will pick up the dirty data immediately and that the CPU will not touch that data before the GPU will. Also, keep the _nocache() primitives to make it easier for people to experiment with these details. There may be more clear-cut cases where non-cached copies can be used, outside of filemap.c. Cc: Salman Qazi <sqazi@google.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/uaccess.h4
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 6f3c603b0d6..6b58367d145 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -41,13 +41,13 @@ static inline void pagefault_enable(void)
#ifndef ARCH_HAS_NOCACHE_UACCESS
static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
- const void __user *from, unsigned long n, unsigned long total)
+ const void __user *from, unsigned long n)
{
return __copy_from_user_inatomic(to, from, n);
}
static inline unsigned long __copy_from_user_nocache(void *to,
- const void __user *from, unsigned long n, unsigned long total)
+ const void __user *from, unsigned long n)
{
return __copy_from_user(to, from, n);
}