From b05e75d611380881e73edc58a20fd8c6bb71720b Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Mon, 16 Mar 2020 15:13:31 -0400 Subject: psi: Fix cpu.pressure for cpu.max and competing cgroups For simplicity, cpu pressure is defined as having more than one runnable task on a given CPU. This works on the system-level, but it has limitations in a cgrouped reality: When cpu.max is in use, it doesn't capture the time in which a task is not executing on the CPU due to throttling. Likewise, it doesn't capture the time in which a competing cgroup is occupying the CPU - meaning it only reflects cgroup-internal competitive pressure, not outside pressure. Enable tracking of currently executing tasks, and then change the definition of cpu pressure in a cgroup from NR_RUNNING > 1 to NR_RUNNING > ON_CPU which will capture the effects of cpu.max as well as competition from outside the cgroup. After this patch, a cgroup running `stress -c 1` with a cpu.max setting of 5000 10000 shows ~50% continuous CPU pressure. Signed-off-by: Johannes Weiner Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200316191333.115523-2-hannes@cmpxchg.org --- kernel/sched/psi.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'kernel/sched/psi.c') diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index 028520702717..50128297a4f9 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -225,7 +225,7 @@ static bool test_state(unsigned int *tasks, enum psi_states state) case PSI_MEM_FULL: return tasks[NR_MEMSTALL] && !tasks[NR_RUNNING]; case PSI_CPU_SOME: - return tasks[NR_RUNNING] > 1; + return tasks[NR_RUNNING] > tasks[NR_ONCPU]; case PSI_NONIDLE: return tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] || tasks[NR_RUNNING]; @@ -695,10 +695,10 @@ static u32 psi_group_change(struct psi_group *group, int cpu, if (!(m & (1 << t))) continue; if (groupc->tasks[t] == 0 && !psi_bug) { - printk_deferred(KERN_ERR "psi: task underflow! cpu=%d t=%d tasks=[%u %u %u] clear=%x set=%x\n", + printk_deferred(KERN_ERR "psi: task underflow! cpu=%d t=%d tasks=[%u %u %u %u] clear=%x set=%x\n", cpu, t, groupc->tasks[0], groupc->tasks[1], groupc->tasks[2], - clear, set); + groupc->tasks[3], clear, set); psi_bug = 1; } groupc->tasks[t]--; @@ -916,9 +916,11 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to) rq = task_rq_lock(task, &rf); - if (task_on_rq_queued(task)) + if (task_on_rq_queued(task)) { task_flags = TSK_RUNNING; - else if (task->in_iowait) + if (task_current(rq, task)) + task_flags |= TSK_ONCPU; + } else if (task->in_iowait) task_flags = TSK_IOWAIT; if (task->flags & PF_MEMSTALL) -- cgit v1.2.3-70-g09d2