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Date: Wed, 13 Jul 2011 13:36:49 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Paul Turner <pjt@...gle.com>, Nikhil Rao <ncrao@...gle.com>,
Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
Cc: linux-kernel <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...e.hu>, Mike Galbraith <efault@....de>
Subject: [RFT][PATCH] sched, cgroup: Optimize load_balance_fair()
Subject: sched, cgroup: Optimize load_balance_fair()
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Wed Jul 13 13:09:25 CEST 2011
Use for_each_leaf_cfs_rq() instead of list_for_each_entry_rcu(), this
achieves that load_balance_fair() only iterates those task_groups that
actually have tasks on busiest, and that we iterate bottom-up, trying to
move light groups before the heavier ones.
No idea if it will actually work out to be beneficial in practice, does
anybody have a cgroup workload that might show a difference one way or
the other?
[ Also move update_h_load to sched_fair.c, loosing #ifdef-ery ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
kernel/sched.c | 32 --------------------------------
kernel/sched_fair.c | 40 +++++++++++++++++++++++++++++++++++-----
2 files changed, 35 insertions(+), 37 deletions(-)
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -1568,38 +1568,6 @@ static unsigned long cpu_avg_load_per_ta
return rq->avg_load_per_task;
}
-#ifdef CONFIG_FAIR_GROUP_SCHED
-
-/*
- * Compute the cpu's hierarchical load factor for each task group.
- * This needs to be done in a top-down fashion because the load of a child
- * group is a fraction of its parents load.
- */
-static int tg_load_down(struct task_group *tg, void *data)
-{
- unsigned long load;
- long cpu = (long)data;
-
- if (!tg->parent) {
- load = cpu_rq(cpu)->load.weight;
- } else {
- load = tg->parent->cfs_rq[cpu]->h_load;
- load *= tg->se[cpu]->load.weight;
- load /= tg->parent->cfs_rq[cpu]->load.weight + 1;
- }
-
- tg->cfs_rq[cpu]->h_load = load;
-
- return 0;
-}
-
-static void update_h_load(long cpu)
-{
- walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
-}
-
-#endif
-
#ifdef CONFIG_PREEMPT
static void double_rq_lock(struct rq *rq1, struct rq *rq2);
Index: linux-2.6/kernel/sched_fair.c
===================================================================
--- linux-2.6.orig/kernel/sched_fair.c
+++ linux-2.6/kernel/sched_fair.c
@@ -2232,11 +2232,43 @@ static void update_shares(int cpu)
struct rq *rq = cpu_rq(cpu);
rcu_read_lock();
+ /*
+ * Iterates the task_group tree in a bottom up fashion, see
+ * list_add_leaf_cfs_rq() for details.
+ */
for_each_leaf_cfs_rq(rq, cfs_rq)
update_shares_cpu(cfs_rq->tg, cpu);
rcu_read_unlock();
}
+/*
+ * Compute the cpu's hierarchical load factor for each task group.
+ * This needs to be done in a top-down fashion because the load of a child
+ * group is a fraction of its parents load.
+ */
+static int tg_load_down(struct task_group *tg, void *data)
+{
+ unsigned long load;
+ long cpu = (long)data;
+
+ if (!tg->parent) {
+ load = cpu_rq(cpu)->load.weight;
+ } else {
+ load = tg->parent->cfs_rq[cpu]->h_load;
+ load *= tg->se[cpu]->load.weight;
+ load /= tg->parent->cfs_rq[cpu]->load.weight + 1;
+ }
+
+ tg->cfs_rq[cpu]->h_load = load;
+
+ return 0;
+}
+
+static void update_h_load(long cpu)
+{
+ walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
+}
+
static unsigned long
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
unsigned long max_load_move,
@@ -2244,14 +2276,12 @@ load_balance_fair(struct rq *this_rq, in
int *all_pinned)
{
long rem_load_move = max_load_move;
- int busiest_cpu = cpu_of(busiest);
- struct task_group *tg;
+ struct cfs_rq *busiest_cfs_rq;
rcu_read_lock();
- update_h_load(busiest_cpu);
+ update_h_load(cpu_of(busiest));
- list_for_each_entry_rcu(tg, &task_groups, list) {
- struct cfs_rq *busiest_cfs_rq = tg->cfs_rq[busiest_cpu];
+ for_each_leaf_cfs_rq(busiest, busiest_cfs_rq) {
unsigned long busiest_h_load = busiest_cfs_rq->h_load;
unsigned long busiest_weight = busiest_cfs_rq->load.weight;
u64 rem_load, moved_load;
--
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