# HG changeset patch
# User Emmanuel Ackaouy <ack@xxxxxxxxxxxxx>
# Node ID 32e4952c063866165d9cab913f67b57f8e78aded
# Parent 8eb8c0085604f3671e062c8d7f0054b42a20986b
[XEN] Optimize credit scheduler load balancing logic
When looking for remote work, only look at or grab a remove CPU's
lock when this CPU is not idling.
Signed-off-by: Emmanuel Ackaouy <ack@xxxxxxxxxxxxx>
---
xen/common/sched_credit.c | 34 +++++++++++++++++++++++++---------
1 files changed, 25 insertions(+), 9 deletions(-)
diff -r 8eb8c0085604 -r 32e4952c0638 xen/common/sched_credit.c
--- a/xen/common/sched_credit.c Mon Nov 06 16:36:51 2006 +0000
+++ b/xen/common/sched_credit.c Mon Nov 06 16:55:56 2006 +0000
@@ -955,8 +955,10 @@ static struct csched_vcpu *
static struct csched_vcpu *
csched_load_balance(int cpu, struct csched_vcpu *snext)
{
+ struct csched_vcpu *speer;
struct csched_pcpu *spc;
- struct csched_vcpu *speer;
+ struct vcpu *peer_vcpu;
+ cpumask_t workers;
int peer_cpu;
if ( snext->pri == CSCHED_PRI_IDLE )
@@ -966,15 +968,23 @@ csched_load_balance(int cpu, struct csch
else
CSCHED_STAT_CRANK(load_balance_other);
+ /*
+ * Peek at non-idling CPUs in the system
+ */
+ cpus_andnot(workers, cpu_online_map, csched_priv.idlers);
+ cpu_clear(cpu, workers);
+
peer_cpu = cpu;
BUG_ON( peer_cpu != snext->vcpu->processor );
- while ( 1 )
- {
- /* For each PCPU in the system starting with our neighbour... */
- peer_cpu = (peer_cpu + 1) % csched_priv.ncpus;
- if ( peer_cpu == cpu )
- break;
+ while ( !cpus_empty(workers) )
+ {
+ /* For each CPU of interest, starting with our neighbour... */
+ peer_cpu = next_cpu(peer_cpu, workers);
+ if ( peer_cpu == NR_CPUS )
+ peer_cpu = first_cpu(workers);
+
+ cpu_clear(peer_cpu, workers);
/*
* Get ahold of the scheduler lock for this peer CPU.
@@ -990,13 +1000,19 @@ csched_load_balance(int cpu, struct csch
}
spc = CSCHED_PCPU(peer_cpu);
+ peer_vcpu = per_cpu(schedule_data, peer_cpu).curr;
+
if ( unlikely(spc == NULL) )
{
CSCHED_STAT_CRANK(steal_peer_down);
speer = NULL;
}
- else if ( is_idle_vcpu(per_cpu(schedule_data, peer_cpu).curr) )
- {
+ else if ( unlikely(is_idle_vcpu(peer_vcpu)) )
+ {
+ /*
+ * Don't steal from an idle CPU's runq because it's about to
+ * pick up work from it itself.
+ */
CSCHED_STAT_CRANK(steal_peer_idle);
speer = NULL;
}
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