diff options
| author | Christian Ehrhardt <ehrhardt@de.ibm.com> | 2006-03-09 17:33:49 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-09 19:47:38 -0800 |
| commit | 96567161de0ceed45cd2eb0e5380e3c797f5c0f4 (patch) | |
| tree | eb1cf052c95b95052e281f9a0d33ea025ce39dc5 /arch | |
| parent | 6a88231fc7da311e4da4ce2011d1a132c80c145a (diff) | |
| download | lwn-96567161de0ceed45cd2eb0e5380e3c797f5c0f4.tar.gz lwn-96567161de0ceed45cd2eb0e5380e3c797f5c0f4.zip | |
[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>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/s390/lib/spinlock.c | 15 |
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; } |