cpumask_weight() is known to be expensive. In Credit2, we use it in
load-balancing, but only for knowing how many CPUs are active in a
runqueue.
Keeping such count in an integer field of the per-runqueue data
structure we have, completely avoids the need for cpumask_weight().
While there, remove as much other uses of it as we can, even if not in
hot-paths.
Signed-off-by: Dario Faggioli <dfaggioli@xxxxxxxx>
---
Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
---
xen/common/sched_credit2.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
index 6958b265fc..7034325243 100644
--- a/xen/common/sched_credit2.c
+++ b/xen/common/sched_credit2.c
@@ -466,6 +466,7 @@ struct csched2_runqueue_data {
spinlock_t lock; /* Lock for this runqueue
*/
struct list_head runq; /* Ordered list of runnable vms */
+ int nr_cpus; /* How many CPUs are sharing this runqueue */
int id; /* ID of this runqueue (-1 if invalid)
*/
int load; /* Instantaneous load (num of non-idle vcpus) */
@@ -2613,8 +2614,8 @@ retry:
if ( st.orqd->b_avgload > load_max )
load_max = st.orqd->b_avgload;
- cpus_max = cpumask_weight(&st.lrqd->active);
- i = cpumask_weight(&st.orqd->active);
+ cpus_max = st.lrqd->nr_cpus;
+ i = st.orqd->nr_cpus;
if ( i > cpus_max )
cpus_max = i;
@@ -3697,7 +3698,7 @@ csched2_dump(const struct scheduler *ops)
"\tinstload = %d\n"
"\taveload = %"PRI_stime" (~%"PRI_stime"%%)\n",
i,
- cpumask_weight(&prv->rqd[i].active),
+ prv->rqd[i].nr_cpus,
nr_cpu_ids, cpumask_bits(&prv->rqd[i].active),
prv->rqd[i].max_weight,
prv->rqd[i].pick_bias,
@@ -3818,6 +3819,9 @@ init_pdata(struct csched2_private *prv, struct
csched2_pcpu *spc,
__cpumask_set_cpu(cpu, &prv->initialized);
__cpumask_set_cpu(cpu, &rqd->smt_idle);
+ rqd->nr_cpus++;
+ ASSERT(cpumask_weight(&rqd->active) == rqd->nr_cpus);
+
/* On the boot cpu we are called before cpu_sibling_mask has been set up.
*/
if ( cpu == 0 && system_state < SYS_STATE_active )
__cpumask_set_cpu(cpu, &csched2_pcpu(cpu)->sibling_mask);
@@ -3829,8 +3833,11 @@ init_pdata(struct csched2_private *prv, struct
csched2_pcpu *spc,
__cpumask_set_cpu(rcpu, &csched2_pcpu(cpu)->sibling_mask);
}
- if ( cpumask_weight(&rqd->active) == 1 )
+ if ( rqd->nr_cpus == 1 )
+ {
+ ASSERT(cpumask_weight(&rqd->active) == 1);
rqd->pick_bias = cpu;
+ }
return spc->runq_id;
}
@@ -3944,8 +3951,12 @@ csched2_deinit_pdata(const struct scheduler *ops, void
*pcpu, int cpu)
__cpumask_clear_cpu(cpu, &rqd->smt_idle);
__cpumask_clear_cpu(cpu, &rqd->active);
- if ( cpumask_empty(&rqd->active) )
+ rqd->nr_cpus--;
+ ASSERT(cpumask_weight(&rqd->active) == rqd->nr_cpus);
+
+ if ( rqd->nr_cpus == 0 )
{
+ ASSERT(cpumask_empty(&rqd->active));
