1. In latencytop source codes, we only have such calling chain: account_scheduler_latency(struct task_struct *task, int usecs, int inter) { if (unlikely(latencytop_enabled)) /* the outtermost check */ __account_scheduler_latency(task, usecs, inter); } __account_scheduler_latency account_global_scheduler_latency if (!latencytop_enabled)
So, the inner check for latencytop_enabled is not necessary at all. 2. In clear_all_latency_tracing and now is called clear_tsk_latency_tracing the check for latencytop_enabled is redundant and buggy to some extent. We have no reason to refuse clearing the /proc/$pid/latency if latencytop_enabled is set to 0, considering that if we use latencytop manually by echo 0 > /proc/sys/kernel/latencytop, then we want to clear /proc/$pid/latency and failed. Aslo we don't have such check in brother function clear_global_latency_tracing. Notes: These changes only visible to users who sets CONFIG_LATENCYTOP and won't change user tool latencytop's behaviors. Signed-off-by: Lin Feng <l...@wangsu.com> --- kernel/latencytop.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/kernel/latencytop.c b/kernel/latencytop.c index 9e794b49791e..897895efafd9 100644 --- a/kernel/latencytop.c +++ b/kernel/latencytop.c @@ -71,9 +71,6 @@ void clear_tsk_latency_tracing(struct task_struct *p) { unsigned long flags; - if (!latencytop_enabled) - return; - raw_spin_lock_irqsave(&latency_lock, flags); memset(&p->latency_record, 0, sizeof(p->latency_record)); p->latency_record_count = 0; @@ -96,9 +93,6 @@ account_global_scheduler_latency(struct task_struct *tsk, int firstnonnull = MAXLR + 1; int i; - if (!latencytop_enabled) - return; - /* skip kernel threads for now */ if (!tsk->mm) return; -- 2.20.1