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authorJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>2008-06-12 10:47:56 +0200
committerIngo Molnar <mingo@elte.hu>2008-06-12 10:47:56 +0200
commitf595ec964daf7f99668039d7303ddedd09a75142 (patch)
tree4ee6679105f0437995ff200f10885598921ae1cd /include
parent5e70b7f3c24468bb1635b295945edb48ecd9656a (diff)
common implementation of iterative div/mod
We have a few instances of the open-coded iterative div/mod loop, used when we don't expcet the dividend to be much bigger than the divisor. Unfortunately modern gcc's have the tendency to strength "reduce" this into a full mod operation, which isn't necessarily any faster, and even if it were, doesn't exist if gcc implements it in libgcc. The workaround is to put a dummy asm statement in the loop to prevent gcc from performing the transformation. This patch creates a single implementation of this loop, and uses it to replace the open-coded versions I know about. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: john stultz <johnstul@us.ibm.com> Cc: Segher Boessenkool <segher@kernel.crashing.org> Cc: Christian Kujau <lists@nerdbynature.de> Cc: Robert Hancock <hancockr@shaw.ca> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include')
-rw-r--r--include/linux/math64.h2
-rw-r--r--include/linux/time.h11
2 files changed, 4 insertions, 9 deletions
diff --git a/include/linux/math64.h b/include/linux/math64.h
index c1a5f81501f..177785e1e4a 100644
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -81,4 +81,6 @@ static inline s64 div_s64(s64 dividend, s32 divisor)
}
#endif
+u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder);
+
#endif /* _LINUX_MATH64_H */
diff --git a/include/linux/time.h b/include/linux/time.h
index d32ef0ad4c0..05f9517a8ed 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -6,6 +6,7 @@
#ifdef __KERNEL__
# include <linux/cache.h>
# include <linux/seqlock.h>
+# include <linux/math64.h>
#endif
#ifndef _STRUCT_TIMESPEC
@@ -172,15 +173,7 @@ extern struct timeval ns_to_timeval(const s64 nsec);
*/
static inline void timespec_add_ns(struct timespec *a, u64 ns)
{
- ns += a->tv_nsec;
- while(unlikely(ns >= NSEC_PER_SEC)) {
- /* The following asm() prevents the compiler from
- * optimising this loop into a modulo operation. */
- asm("" : "+r"(ns));
-
- ns -= NSEC_PER_SEC;
- a->tv_sec++;
- }
+ a->tv_sec += iter_div_u64_rem(a->tv_nsec + ns, NSEC_PER_SEC, &ns);
a->tv_nsec = ns;
}
#endif /* __KERNEL__ */