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authorChristian Ehrhardt <ehrhardt@de.ibm.com>2006-03-09 17:33:49 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-09 19:47:38 -0800
commit96567161de0ceed45cd2eb0e5380e3c797f5c0f4 (patch)
treeeb1cf052c95b95052e281f9a0d33ea025ce39dc5
parent6a88231fc7da311e4da4ce2011d1a132c80c145a (diff)
downloadlinux-stericsson-96567161de0ceed45cd2eb0e5380e3c797f5c0f4.tar.gz
[PATCH] s390: Increase spinlock retry code performance
Currently the code tries up to spin_retry times to grab a lock using the cs instruction. The cs instruction has exclusive access to a memory region and therefore invalidates the appropiate cache line of all other cpus. If there is contention on a lock this leads to cache line trashing. This can be avoided if we first check wether a cs instruction is likely to succeed before the instruction gets actually executed. Signed-off-by: Christian Ehrhardt <ehrhardt@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/s390/lib/spinlock.c15
1 files changed, 13 insertions, 2 deletions
diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index 60f80a4eed4e..b9b7958a226a 100644
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -2,8 +2,7 @@
* arch/s390/lib/spinlock.c
* Out of line spinlock code.
*
- * S390 version
- * Copyright (C) 2004 IBM Deutschland Entwicklung GmbH, IBM Corporation
+ * Copyright (C) IBM Corp. 2004, 2006
* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
*/
@@ -44,6 +43,8 @@ _raw_spin_lock_wait(raw_spinlock_t *lp, unsigned int pc)
_diag44();
count = spin_retry;
}
+ if (__raw_spin_is_locked(lp))
+ continue;
if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
return;
}
@@ -56,6 +57,8 @@ _raw_spin_trylock_retry(raw_spinlock_t *lp, unsigned int pc)
int count = spin_retry;
while (count-- > 0) {
+ if (__raw_spin_is_locked(lp))
+ continue;
if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
return 1;
}
@@ -74,6 +77,8 @@ _raw_read_lock_wait(raw_rwlock_t *rw)
_diag44();
count = spin_retry;
}
+ if (!__raw_read_can_lock(rw))
+ continue;
old = rw->lock & 0x7fffffffU;
if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)
return;
@@ -88,6 +93,8 @@ _raw_read_trylock_retry(raw_rwlock_t *rw)
int count = spin_retry;
while (count-- > 0) {
+ if (!__raw_read_can_lock(rw))
+ continue;
old = rw->lock & 0x7fffffffU;
if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)
return 1;
@@ -106,6 +113,8 @@ _raw_write_lock_wait(raw_rwlock_t *rw)
_diag44();
count = spin_retry;
}
+ if (!__raw_write_can_lock(rw))
+ continue;
if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
return;
}
@@ -118,6 +127,8 @@ _raw_write_trylock_retry(raw_rwlock_t *rw)
int count = spin_retry;
while (count-- > 0) {
+ if (!__raw_write_can_lock(rw))
+ continue;
if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
return 1;
}