Author: mav
Date: Wed Oct 9 18:29:06 2013
New Revision: 256208
URL: http://svnweb.freebsd.org/changeset/base/256208
Log:
MFC r255363:
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:
stable/9/sys/kern/sched_ule.c
Modified: stable/9/sys/kern/sched_ule.c
==============================================================================
--- stable/9/sys/kern/sched_ule.c Wed Oct 9 18:23:30 2013
(r256207)
+++ stable/9/sys/kern/sched_ule.c Wed Oct 9 18:29:06 2013
(r256208)
@@ -632,10 +632,14 @@ 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;
@@ -660,6 +664,7 @@ 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);
@@ -707,8 +712,11 @@ 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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