Author: mav
Date: Sat Sep 7 15:16:30 2013
New Revision: 255363
URL: http://svnweb.freebsd.org/changeset/base/255363
Log:
Micro-optimize cpu_search(), allowing compiler to use more efficient inline
ffsl() implementation, when it is available, instead of homegrown iteration.
On dual-E5645 amd64 system (2x6x2 cores) under heavy I/O load that reduces
time spent inside cpu_search() from 19% to 13%, while IOPS increased by 5%.
Modified:
head/sys/kern/sched_ule.c
Modified: head/sys/kern/sched_ule.c
==============================================================================
--- head/sys/kern/sched_ule.c Sat Sep 7 14:15:13 2013 (r255362)
+++ head/sys/kern/sched_ule.c Sat Sep 7 15:16:30 2013 (r255363)
@@ -667,10 +667,14 @@ cpu_search(const struct cpu_group *cg, s
}
/* Iterate through the child CPU groups and then remaining CPUs. */
- for (i = cg->cg_children, cpu = mp_maxid; i >= 0; ) {
+ for (i = cg->cg_children, cpu = mp_maxid; ; ) {
if (i == 0) {
+#ifdef HAVE_INLINE_FFSL
+ cpu = CPU_FFS(&cpumask) - 1;
+#else
while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask))
cpu--;
+#endif
if (cpu < 0)
break;
child = NULL;
@@ -695,6 +699,7 @@ cpu_search(const struct cpu_group *cg, s
break;
}
} else { /* Handle child CPU. */
+ CPU_CLR(cpu, &cpumask);
tdq = TDQ_CPU(cpu);
load = tdq->tdq_load * 256;
rndptr = DPCPU_PTR(randomval);
@@ -742,8 +747,11 @@ cpu_search(const struct cpu_group *cg, s
i--;
if (i == 0 && CPU_EMPTY(&cpumask))
break;
- } else
+ }
+#ifndef HAVE_INLINE_FFSL
+ else
cpu--;
+#endif
}
return (total);
}
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