Hi Peter, On 2021/3/20 23:34, Peter Zijlstra wrote: > On Fri, Mar 19, 2021 at 04:32:48PM -0400, Joel Fernandes (Google) wrote: >> @@ -7530,8 +7543,9 @@ int can_migrate_task(struct task_struct *p, struct >> lb_env *env) >> * We do not migrate tasks that are: >> * 1) throttled_lb_pair, or >> * 2) cannot be migrated to this CPU due to cpus_ptr, or >> - * 3) running (obviously), or >> - * 4) are cache-hot on their current CPU. >> + * 3) task's cookie does not match with this CPU's core cookie >> + * 4) running (obviously), or >> + * 5) are cache-hot on their current CPU. >> */ >> if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu)) >> return 0; >> @@ -7566,6 +7580,13 @@ int can_migrate_task(struct task_struct *p, struct >> lb_env *env) >> return 0; >> } >> >> + /* >> + * Don't migrate task if the task's cookie does not match >> + * with the destination CPU's core cookie. >> + */ >> + if (!sched_core_cookie_match(cpu_rq(env->dst_cpu), p)) >> + return 0; >> + >> /* Record that we found atleast one task that could run on dst_cpu */ >> env->flags &= ~LBF_ALL_PINNED; >> > > This one is too strong.. persistent imbalance should be able to override > it. >
IIRC, this change can avoid the following scenario: One sysbench cpu thread(cookieA) and sysbench mysql thread(cookieB) running on the two siblings of core_1, the other sysbench cpu thread(cookieA) and sysbench mysql thread(cookieB) running on the two siblings of core2, which causes 50% force idle. This is not an imbalance case. Thanks, -Aubrey
