Add cpu_relax() to tasklet_unlock_wait() loop.
I kept barrier() since it is said to still be required, in various older
postings.
Took care of kernel style formatting.
Tested on 2.6.17-mm1.
This is the first patch within a set, which aims to improve P4 HT performance
a bit:
these SMT CPUs want a rep nop (pause) (as done by cpu_relax()) when
busy-polling, in order to free pipeline resources for the SMT CPU sibling.
During I/O polling cpu_relax() will help for non-P4 CPUs, too (reduce
power consumption there).
Signed-off-by: Andreas Mohr <[email protected]>
diff -urN linux-2.6.17-mm1.orig/include/linux/interrupt.h linux-2.6.17-mm1.my/include/linux/interrupt.h
--- linux-2.6.17-mm1.orig/include/linux/interrupt.h 2006-06-21 14:28:19.000000000 +0200
+++ linux-2.6.17-mm1.my/include/linux/interrupt.h 2006-06-21 21:34:12.000000000 +0200
@@ -227,7 +227,10 @@
static inline void tasklet_unlock_wait(struct tasklet_struct *t)
{
- while (test_bit(TASKLET_STATE_RUN, &(t)->state)) { barrier(); }
+ while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {
+ barrier();
+ cpu_relax();
+ }
}
#else
#define tasklet_trylock(t) 1
-
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