diff options
| author | Phil Auld <pauld@redhat.com> | 2023-07-12 09:33:57 -0400 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2023-08-02 16:19:26 +0200 |
| commit | 88c56cfeaec4642aee8aac58b38d5708c6aae0d3 (patch) | |
| tree | a931bedfa512ff5828f15bf56d50158b030a1b60 /kernel/sched/sched.h | |
| parent | c98c18270be115678f4295b10a5af5dcc9c4efa0 (diff) | |
sched/fair: Block nohz tick_stop when cfs bandwidth in use
CFS bandwidth limits and NOHZ full don't play well together. Tasks
can easily run well past their quotas before a remote tick does
accounting. This leads to long, multi-period stalls before such
tasks can run again. Currently, when presented with these conflicting
requirements the scheduler is favoring nohz_full and letting the tick
be stopped. However, nohz tick stopping is already best-effort, there
are a number of conditions that can prevent it, whereas cfs runtime
bandwidth is expected to be enforced.
Make the scheduler favor bandwidth over stopping the tick by setting
TICK_DEP_BIT_SCHED when the only running task is a cfs task with
runtime limit enabled. We use cfs_b->hierarchical_quota to
determine if the task requires the tick.
Add check in pick_next_task_fair() as well since that is where
we have a handle on the task that is actually going to be running.
Add check in sched_can_stop_tick() to cover some edge cases such
as nr_running going from 2->1 and the 1 remains the running task.
Reviewed-By: Ben Segall <bsegall@google.com>
Signed-off-by: Phil Auld <pauld@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230712133357.381137-3-pauld@redhat.com
Diffstat (limited to 'kernel/sched/sched.h')
| -rw-r--r-- | kernel/sched/sched.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 602de71b48e1..19af1766df2d 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -459,6 +459,7 @@ extern void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b, struct cfs_bandwidth extern void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b); extern void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b); extern void unthrottle_cfs_rq(struct cfs_rq *cfs_rq); +extern bool cfs_task_bw_constrained(struct task_struct *p); extern void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq, struct sched_rt_entity *rt_se, int cpu, @@ -494,6 +495,7 @@ static inline void set_task_rq_fair(struct sched_entity *se, #else /* CONFIG_CGROUP_SCHED */ struct cfs_bandwidth { }; +static inline bool cfs_task_bw_constrained(struct task_struct *p) { return false; } #endif /* CONFIG_CGROUP_SCHED */ |