Messages in this thread Patch in this message | | | Date | Tue, 22 Jul 2014 14:45:59 -0400 | From | Rik van Riel <> | Subject | [PATCH] sched: make update_sd_pick_busiest return true on a busier sd |
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Currently update_sd_pick_busiest only returns true when an sd is overloaded, or for SD_ASYM_PACKING when a domain is busier than average and a higher numbered domain than the target.
This breaks load balancing between domains that are not overloaded, in the !SD_ASYM_PACKING case. This patch makes update_sd_pick_busiest return true when the busiest sd yet is encountered.
On a 4 node system, this seems to result in the load balancer finally putting 1 thread of a 4 thread test run of "perf bench numa mem" on each node, where before the load was generally not spread across all nodes.
Behaviour for SD_ASYM_PACKING does not seem to match the comment, in that groups with below average load average are ignored, but I have no hardware to test that so I have left the behaviour of that code unchanged.
Cc: mikey@neuling.org Cc: peterz@infradead.org Signed-off-by: Rik van Riel <riel@redhat.com> --- kernel/sched/fair.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index fea7d33..ff4ddba 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5942,16 +5942,20 @@ static bool update_sd_pick_busiest(struct lb_env *env, * numbered CPUs in the group, therefore mark all groups * higher than ourself as busy. */ - if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running && - env->dst_cpu < group_first_cpu(sg)) { - if (!sds->busiest) - return true; + if (env->sd->flags & SD_ASYM_PACKING) { + if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) { + if (!sds->busiest) + return true; - if (group_first_cpu(sds->busiest) > group_first_cpu(sg)) - return true; + if (group_first_cpu(sds->busiest) > group_first_cpu(sg)) + return true; + } + + return false; } - return false; + /* See above: sgs->avg_load > sds->busiest_stat.avg_load */ + return true; } #ifdef CONFIG_NUMA_BALANCING
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