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authorNick Piggin <nickpiggin@yahoo.com.au>2005-09-10 00:26:19 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-10 10:06:23 -0700
commit5969fe0618051e8577316555a81a6e44b7b7d640 (patch)
tree09ca92684811017901bb08d8d3a76c52022ef34d /kernel
parente17224bf1d01b461ec02a60f5a9b7657a89bdd23 (diff)
[PATCH] sched: HT optimisation
If an idle sibling of an HT queue encounters a busy sibling, then make higher level load balancing of the non-idle variety. Performance of multiprocessor HT systems with low numbers of tasks (generally < number of virtual CPUs) can be significantly worse than the exact same workloads when running in non-HT mode. The reason is largely due to poor scheduling behaviour. This patch improves the situation, making the performance gap far less significant on one problematic test case (tbench). Signed-off-by: Nick Piggin <npiggin@suse.de> Acked-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched.c34
1 files changed, 28 insertions, 6 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 8535e5c68f5b..46fdd0bb1ed6 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1906,7 +1906,7 @@ out:
*/
static struct sched_group *
find_busiest_group(struct sched_domain *sd, int this_cpu,
- unsigned long *imbalance, enum idle_type idle)
+ unsigned long *imbalance, enum idle_type idle, int *sd_idle)
{
struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups;
unsigned long max_load, avg_load, total_load, this_load, total_pwr;
@@ -1931,6 +1931,9 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
avg_load = 0;
for_each_cpu_mask(i, group->cpumask) {
+ if (*sd_idle && !idle_cpu(i))
+ *sd_idle = 0;
+
/* Bias balancing toward cpus of our domain */
if (local_group)
load = target_load(i, load_idx);
@@ -2074,10 +2077,14 @@ static int load_balance(int this_cpu, runqueue_t *this_rq,
unsigned long imbalance;
int nr_moved, all_pinned = 0;
int active_balance = 0;
+ int sd_idle = 0;
+
+ if (idle != NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER)
+ sd_idle = 1;
schedstat_inc(sd, lb_cnt[idle]);
- group = find_busiest_group(sd, this_cpu, &imbalance, idle);
+ group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle);
if (!group) {
schedstat_inc(sd, lb_nobusyg[idle]);
goto out_balanced;
@@ -2150,6 +2157,8 @@ static int load_balance(int this_cpu, runqueue_t *this_rq,
sd->balance_interval *= 2;
}
+ if (!nr_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER)
+ return -1;
return nr_moved;
out_balanced:
@@ -2161,6 +2170,8 @@ out_balanced:
(sd->balance_interval < sd->max_interval))
sd->balance_interval *= 2;
+ if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
+ return -1;
return 0;
}
@@ -2178,9 +2189,13 @@ static int load_balance_newidle(int this_cpu, runqueue_t *this_rq,
runqueue_t *busiest = NULL;
unsigned long imbalance;
int nr_moved = 0;
+ int sd_idle = 0;
+
+ if (sd->flags & SD_SHARE_CPUPOWER)
+ sd_idle = 1;
schedstat_inc(sd, lb_cnt[NEWLY_IDLE]);
- group = find_busiest_group(sd, this_cpu, &imbalance, NEWLY_IDLE);
+ group = find_busiest_group(sd, this_cpu, &imbalance, NEWLY_IDLE, &sd_idle);
if (!group) {
schedstat_inc(sd, lb_nobusyg[NEWLY_IDLE]);
goto out_balanced;
@@ -2205,15 +2220,19 @@ static int load_balance_newidle(int this_cpu, runqueue_t *this_rq,
spin_unlock(&busiest->lock);
}
- if (!nr_moved)
+ if (!nr_moved) {
schedstat_inc(sd, lb_failed[NEWLY_IDLE]);
- else
+ if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
+ return -1;
+ } else
sd->nr_balance_failed = 0;
return nr_moved;
out_balanced:
schedstat_inc(sd, lb_balanced[NEWLY_IDLE]);
+ if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
+ return -1;
sd->nr_balance_failed = 0;
return 0;
}
@@ -2338,7 +2357,10 @@ static void rebalance_tick(int this_cpu, runqueue_t *this_rq,
if (j - sd->last_balance >= interval) {
if (load_balance(this_cpu, this_rq, sd, idle)) {
- /* We've pulled tasks over so no longer idle */
+ /* We've pulled tasks over so either we're no
+ * longer idle, or one of our SMT siblings is
+ * not idle.
+ */
idle = NOT_IDLE;
}
sd->last_balance += interval;

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