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Microoptimize cpu_search().

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According to profiling, it makes one take 6% of CPU time on hackbench
with its million of context switches per second, instead of 8% before.
This commit is contained in:
mav 2012-04-09 18:24:58 +00:00
parent 628004ddfb
commit e1ffe54fb7
1 changed files with 28 additions and 24 deletions
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52
sys/kern/sched_ule.c
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@ -594,32 +594,34 @@ cpu_search(const struct cpu_group *cg, struct cpu_search *low,
cpuset_t cpumask;
struct cpu_group *child;
struct tdq *tdq;
int cpu, i, hload, lload, load, total, rnd;
int cpu, i, hload, lload, load, total, rnd, *rndptr;
total = 0;
cpumask = cg->cg_mask;
if (match & CPU_SEARCH_LOWEST) {
lload = INT_MAX;
low->cs_load = INT_MAX;
lgroup = *low;
}
if (match & CPU_SEARCH_HIGHEST) {
hload = -1;
high->cs_load = -1;
hload = INT_MIN;
hgroup = *high;
}
/* Iterate through the child CPU groups and then remaining CPUs. */
for (i = 0, cpu = 0; i <= cg->cg_children; ) {
if (i >= cg->cg_children) {
while (cpu <= mp_maxid && !CPU_ISSET(cpu, &cpumask))
cpu++;
if (cpu > mp_maxid)
for (i = cg->cg_children, cpu = mp_maxid; i >= 0; ) {
if (i == 0) {
while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask))
cpu--;
if (cpu < 0)
break;
child = NULL;
} else
child = &cg->cg_child[i];
child = &cg->cg_child[i - 1];
if (match & CPU_SEARCH_LOWEST)
lgroup.cs_cpu = -1;
if (match & CPU_SEARCH_HIGHEST)
hgroup.cs_cpu = -1;
if (child) { /* Handle child CPU group. */
CPU_NAND(&cpumask, &child->cg_mask);
switch (match) {
@ -636,23 +638,23 @@ cpu_search(const struct cpu_group *cg, struct cpu_search *low,
} else { /* Handle child CPU. */
tdq = TDQ_CPU(cpu);
load = tdq->tdq_load * 256;
rnd = DPCPU_SET(randomval,
DPCPU_GET(randomval) * 69069 + 5) >> 26;
rndptr = DPCPU_PTR(randomval);
rnd = (*rndptr = *rndptr * 69069 + 5) >> 26;
if (match & CPU_SEARCH_LOWEST) {
if (cpu == low->cs_prefer)
load -= 64;
/* If that CPU is allowed and get data. */
if (CPU_ISSET(cpu, &lgroup.cs_mask) &&
tdq->tdq_lowpri > lgroup.cs_pri &&
tdq->tdq_load <= lgroup.cs_limit) {
if (tdq->tdq_lowpri > lgroup.cs_pri &&
tdq->tdq_load <= lgroup.cs_limit &&
CPU_ISSET(cpu, &lgroup.cs_mask)) {
lgroup.cs_cpu = cpu;
lgroup.cs_load = load - rnd;
}
}
if (match & CPU_SEARCH_HIGHEST)
if (CPU_ISSET(cpu, &hgroup.cs_mask) &&
tdq->tdq_load >= hgroup.cs_limit &&
tdq->tdq_transferable) {
if (tdq->tdq_load >= hgroup.cs_limit &&
tdq->tdq_transferable &&
CPU_ISSET(cpu, &hgroup.cs_mask)) {
hgroup.cs_cpu = cpu;
hgroup.cs_load = load - rnd;
}
@ -661,7 +663,7 @@ cpu_search(const struct cpu_group *cg, struct cpu_search *low,
/* We have info about child item. Compare it. */
if (match & CPU_SEARCH_LOWEST) {
if (lgroup.cs_load != INT_MAX &&
if (lgroup.cs_cpu >= 0 &&
(load < lload ||
(load == lload && lgroup.cs_load < low->cs_load))) {
lload = load;
@ -670,17 +672,19 @@ cpu_search(const struct cpu_group *cg, struct cpu_search *low,
}
}
if (match & CPU_SEARCH_HIGHEST)
if (hgroup.cs_load >= 0 &&
if (hgroup.cs_cpu >= 0 &&
(load > hload ||
(load == hload && hgroup.cs_load > high->cs_load))) {
hload = load;
high->cs_cpu = hgroup.cs_cpu;
high->cs_load = hgroup.cs_load;
}
if (child)
i++;
else
cpu++;
if (child) {
i--;
if (i == 0 && CPU_EMPTY(&cpumask))
break;
} else
cpu--;
}
return (total);
}