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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2005-07-27 11:44:57 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-07-27 16:26:04 -0700
commit951f22d5b1f0eaae35dafc669e3774a0c2084d10 (patch)
tree66c0131b576dadb98026da11d624df453c4c9a7c /kernel/sysctl.c
parent8449d003f323ca7a00eec38905d984ba5ec83a29 (diff)
downloadlwn-951f22d5b1f0eaae35dafc669e3774a0c2084d10.tar.gz
lwn-951f22d5b1f0eaae35dafc669e3774a0c2084d10.zip
[PATCH] s390: spin lock retry
Split spin lock and r/w lock implementation into a single try which is done inline and an out of line function that repeatedly tries to get the lock before doing the cpu_relax(). Add a system control to set the number of retries before a cpu is yielded. The reason for the spin lock retry is that the diagnose 0x44 that is used to give up the virtual cpu is quite expensive. For spin locks that are held only for a short period of time the costs of the diagnoses outweights the savings for spin locks that are held for a longer timer. The default retry count is 1000. 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 'kernel/sysctl.c')
-rw-r--r--kernel/sysctl.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index e60b9c36f1f0..3e0bbee549ea 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -114,6 +114,7 @@ extern int unaligned_enabled;
extern int sysctl_ieee_emulation_warnings;
#endif
extern int sysctl_userprocess_debug;
+extern int spin_retry;
#endif
extern int sysctl_hz_timer;
@@ -647,7 +648,16 @@ static ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = &proc_dointvec,
},
-
+#if defined(CONFIG_ARCH_S390)
+ {
+ .ctl_name = KERN_SPIN_RETRY,
+ .procname = "spin_retry",
+ .data = &spin_retry,
+ .maxlen = sizeof (int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
+#endif
{ .ctl_name = 0 }
};