Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Josef Bacik <> | Subject | [PATCH 7/7] sched/fair: don't wake affine recently load balanced tasks | Date | Fri, 14 Jul 2017 13:21:04 +0000 |
| |
From: Josef Bacik <jbacik@fb.com>
The wake affinity logic will move tasks between two cpu's that appear to be loaded equally at the current time, with a slight bias towards cache locality. However on a heavily loaded system the load balancer has a better insight into what needs to be moved around, so instead keep track of the last time a task was migrated by the load balancer. If it was recent, opt to let the process stay on it's current CPU (or an idle sibling).
Signed-off-by: Josef Bacik <jbacik@fb.com> --- include/linux/sched.h | 1 + kernel/sched/fair.c | 11 +++++++++++ 2 files changed, 12 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h index 1a0eadd..d872780 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -528,6 +528,7 @@ struct task_struct { unsigned long wakee_flip_decay_ts; struct task_struct *last_wakee; + unsigned long last_balance_ts; int wake_cpu; #endif int on_rq; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 034d5df..6a98a38 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5604,6 +5604,16 @@ static int wake_wide(struct task_struct *p) unsigned int slave = p->wakee_flips; int factor = this_cpu_read(sd_llc_size); + /* + * If we've balanced this task recently we don't want to undo all of + * that hard work by the load balancer and move it to the current cpu. + * Constantly overriding the load balancers decisions is going to make + * it question its purpose in life and give it anxiety and self worth + * issues, and nobody wants that. + */ + if (time_before(jiffies, p->last_balance_ts + HZ)) + return 1; + if (master < slave) swap(master, slave); if (slave < factor || master < slave * factor) @@ -7097,6 +7107,7 @@ static int detach_tasks(struct lb_env *env) goto next; detach_task(p, env); + p->last_balance_ts = jiffies; list_add(&p->se.group_node, &env->tasks); detached++; -- 2.9.3
| ![\](/images/icornerr.gif) |