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sched/numa: Use effective_load() to balance NUMA loads 

When CONFIG_FAIR_GROUP_SCHED is enabled, the load that a task places
on a CPU is determined by the group the task is in. The active groups
on the source and destination CPU can be different, resulting in a
different load contribution by the same task at its source and at its
destination. As a result, the load needs to be calculated separately
for each CPU, instead of estimated once with task_h_load().

Getting this calculation right allows some workloads to converge,
where previously the last thread could get stuck on another node,
without being able to migrate to its final destination.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: mgorman@suse.de
Cc: chegu_vinod@hp.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1403538378-31571-3-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Rik van Riel 2014-06-23 11:46:14 -04:00 committed by Ingo Molnar
parent 28a2174519
commit 6dc1a672ab
1 changed files with 14 additions and 6 deletions
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20
kernel/sched/fair.c
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@ -1151,6 +1151,7 @@ static void task_numa_compare(struct task_numa_env *env,
struct rq *src_rq = cpu_rq(env->src_cpu);
struct rq *dst_rq = cpu_rq(env->dst_cpu);
struct task_struct *cur;
struct task_group *tg;
long src_load, dst_load;
long load;
long imp = (groupimp > 0) ? groupimp : taskimp;
@ -1225,14 +1226,21 @@ static void task_numa_compare(struct task_numa_env *env,
* In the overloaded case, try and keep the load balanced.
*/
balance:
load = task_h_load(env->p);
dst_load = env->dst_stats.load + load;
src_load = env->src_stats.load - load;
src_load = env->src_stats.load;
dst_load = env->dst_stats.load;
/* Calculate the effect of moving env->p from src to dst. */
load = env->p->se.load.weight;
tg = task_group(env->p);
src_load += effective_load(tg, env->src_cpu, -load, -load);
dst_load += effective_load(tg, env->dst_cpu, load, load);
if (cur) {
load = task_h_load(cur);
dst_load -= load;
src_load += load;
/* Cur moves in the opposite direction. */
load = cur->se.load.weight;
tg = task_group(cur);
src_load += effective_load(tg, env->src_cpu, load, load);
dst_load += effective_load(tg, env->dst_cpu, -load, -load);
}
if (load_too_imbalanced(src_load, dst_load, env))