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authorJohannes Weiner <hannes@cmpxchg.org>2020-03-16 15:13:31 -0400
committerPeter Zijlstra <peterz@infradead.org>2020-03-20 13:06:18 +0100
commitb05e75d611380881e73edc58a20fd8c6bb71720b (patch)
tree3d641b57b42e934d7518f22a13f3a74cd76f6ff7 /kernel/sched/psi.c
parent46a87b3851f0d6eb05e6d83d5c5a30df0eca8f76 (diff)
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 <hannes@cmpxchg.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200316191333.115523-2-hannes@cmpxchg.org
Diffstat (limited to 'kernel/sched/psi.c')
-rw-r--r--kernel/sched/psi.c12
1 files changed, 7 insertions, 5 deletions
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)