From: Chuck Ebbert <76306.1226@compuserve.com>
To: linux-kernel <linux-kernel@vger.kernel.org>
Cc: Andrew Morton <akpm@osdl.org>, Ingo Molnar <mingo@elte.hu>,
Linus Torvalds <torvalds@osdl.org>
Subject: [patch] spinlock_debug: don't recompute (jiffies_per_loop * HZ) in spinloop
Date: Fri, 21 Jul 2006 18:30:57 -0400 [thread overview]
Message-ID: <200607211834_MC3-1-C5BD-B57D@compuserve.com> (raw)
In spinlock_debug.c, the spinloops call __delay() on every iteration.
Because that is an external function, (jiffies_per_loop * HZ), the
loop's iteration limit, gets recomputed every time. Caching it
explicitly prevents that.
Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
---
__delay() should really be declared __attribute_pure.
--- 2.6.18-rc2-64-numa.orig/lib/spinlock_debug.c
+++ 2.6.18-rc2-64-numa/lib/spinlock_debug.c
@@ -99,11 +99,12 @@ static inline void debug_spin_unlock(spi
static void __spin_lock_debug(spinlock_t *lock)
{
- int print_once = 1;
u64 i;
+ u64 loops = loops_per_jiffy * HZ;
+ int print_once = 1;
for (;;) {
- for (i = 0; i < loops_per_jiffy * HZ; i++) {
+ for (i = 0; i < loops; i++) {
if (__raw_spin_trylock(&lock->raw_lock))
return;
__delay(1);
@@ -164,11 +165,12 @@ static void rwlock_bug(rwlock_t *lock, c
static void __read_lock_debug(rwlock_t *lock)
{
- int print_once = 1;
u64 i;
+ u64 loops = loops_per_jiffy * HZ;
+ int print_once = 1;
for (;;) {
- for (i = 0; i < loops_per_jiffy * HZ; i++) {
+ for (i = 0; i < loops; i++) {
if (__raw_read_trylock(&lock->raw_lock))
return;
__delay(1);
@@ -237,11 +239,12 @@ static inline void debug_write_unlock(rw
static void __write_lock_debug(rwlock_t *lock)
{
- int print_once = 1;
u64 i;
+ u64 loops = loops_per_jiffy * HZ;
+ int print_once = 1;
for (;;) {
- for (i = 0; i < loops_per_jiffy * HZ; i++) {
+ for (i = 0; i < loops; i++) {
if (__raw_write_trylock(&lock->raw_lock))
return;
__delay(1);
--
Chuck
reply other threads:[~2006-07-21 22:36 UTC|newest]
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