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authorChristian Ehrhardt <ehrhardt@de.ibm.com>2006-03-09 20:33:49 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-09 22:47:38 -0500
commit96567161de0ceed45cd2eb0e5380e3c797f5c0f4 (patch)
treeeb1cf052c95b95052e281f9a0d33ea025ce39dc5
parent6a88231fc7da311e4da4ce2011d1a132c80c145a (diff)
[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 @@
2 * arch/s390/lib/spinlock.c 2 * arch/s390/lib/spinlock.c
3 * Out of line spinlock code. 3 * Out of line spinlock code.
4 * 4 *
5 * S390 version 5 * Copyright (C) IBM Corp. 2004, 2006
6 * Copyright (C) 2004 IBM Deutschland Entwicklung GmbH, IBM Corporation
7 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com) 6 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
8 */ 7 */
9 8
@@ -44,6 +43,8 @@ _raw_spin_lock_wait(raw_spinlock_t *lp, unsigned int pc)
44 _diag44(); 43 _diag44();
45 count = spin_retry; 44 count = spin_retry;
46 } 45 }
46 if (__raw_spin_is_locked(lp))
47 continue;
47 if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0) 48 if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
48 return; 49 return;
49 } 50 }
@@ -56,6 +57,8 @@ _raw_spin_trylock_retry(raw_spinlock_t *lp, unsigned int pc)
56 int count = spin_retry; 57 int count = spin_retry;
57 58
58 while (count-- > 0) { 59 while (count-- > 0) {
60 if (__raw_spin_is_locked(lp))
61 continue;
59 if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0) 62 if (_raw_compare_and_swap(&lp->lock, 0, pc) == 0)
60 return 1; 63 return 1;
61 } 64 }
@@ -74,6 +77,8 @@ _raw_read_lock_wait(raw_rwlock_t *rw)
74 _diag44(); 77 _diag44();
75 count = spin_retry; 78 count = spin_retry;
76 } 79 }
80 if (!__raw_read_can_lock(rw))
81 continue;
77 old = rw->lock & 0x7fffffffU; 82 old = rw->lock & 0x7fffffffU;
78 if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old) 83 if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)
79 return; 84 return;
@@ -88,6 +93,8 @@ _raw_read_trylock_retry(raw_rwlock_t *rw)
88 int count = spin_retry; 93 int count = spin_retry;
89 94
90 while (count-- > 0) { 95 while (count-- > 0) {
96 if (!__raw_read_can_lock(rw))
97 continue;
91 old = rw->lock & 0x7fffffffU; 98 old = rw->lock & 0x7fffffffU;
92 if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old) 99 if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)
93 return 1; 100 return 1;
@@ -106,6 +113,8 @@ _raw_write_lock_wait(raw_rwlock_t *rw)
106 _diag44(); 113 _diag44();
107 count = spin_retry; 114 count = spin_retry;
108 } 115 }
116 if (!__raw_write_can_lock(rw))
117 continue;
109 if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0) 118 if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
110 return; 119 return;
111 } 120 }
@@ -118,6 +127,8 @@ _raw_write_trylock_retry(raw_rwlock_t *rw)
118 int count = spin_retry; 127 int count = spin_retry;
119 128
120 while (count-- > 0) { 129 while (count-- > 0) {
130 if (!__raw_write_can_lock(rw))
131 continue;
121 if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0) 132 if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
122 return 1; 133 return 1;
123 } 134 }