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x86: usercopy: check for total size when deciding non-temporal cutoff

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Impact: make more types of copies non-temporal

This change makes the following simple fix:

  30d697f: x86: fix performance regression in write() syscall

A bit more sophisticated: we check the 'total' number of bytes
written to decide whether to copy in a cached or a non-temporal
way.

This will for example cause the tail (modulo 4096 bytes) chunk
of a large write() to be non-temporal too - not just the page-sized
chunks.

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>
This commit is contained in:
Ingo Molnar 2009-02-25 08:22:20 +01:00
parent 3255aa2eb6
commit 95108fa34a
1 changed files with 2 additions and 2 deletions
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4
arch/x86/include/asm/uaccess_64.h
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@ -198,7 +198,7 @@ static inline int __copy_from_user_nocache(void *dst, const void __user *src,
* non-temporal stores here. Smaller writes get handled
* via regular __copy_from_user():
*/
if (likely(size >= PAGE_SIZE))
if (likely(total >= PAGE_SIZE))
return __copy_user_nocache(dst, src, size, 1);
else
return __copy_from_user(dst, src, size);
@ -207,7 +207,7 @@ static inline int __copy_from_user_nocache(void *dst, const void __user *src,
static inline int __copy_from_user_inatomic_nocache(void *dst,
const void __user *src, unsigned size, unsigned total)
{
if (likely(size >= PAGE_SIZE))
if (likely(total >= PAGE_SIZE))
return __copy_user_nocache(dst, src, size, 0);
else
return __copy_from_user_inatomic(dst, src, size);