linux-kernel - [PATCH v2 4/6] sched: introduce task block time in schedstats

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Date:   Sat, 27 Mar 2021 18:12:51 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     mgorman@...e.de, mingo@...hat.com, peterz@...radead.org,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        bristot@...hat.com
Cc:     linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
        Yafang Shao <laoar.shao@...il.com>
Subject: [PATCH v2 4/6] sched: introduce task block time in schedstats

Currently in schedstats we have sum_sleep_runtime and iowait_sum, but
there's no metric to show how long the task is in D state.  Once a task in
D state, it means the task is blocked in the kernel, for example the
task may be waiting for a mutex. The D state is more frequent than
iowait, and it is more critital than S state. So it is worth to add a
metric to measure it.

Signed-off-by: Yafang Shao <laoar.shao@...il.com>
---
 include/linux/sched.h | 2 ++
 kernel/sched/debug.c  | 6 ++++--
 kernel/sched/stats.c  | 1 +
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index b687bb38897b..2b885481b8bf 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -428,6 +428,8 @@ struct sched_statistics {
 
 	u64				block_start;
 	u64				block_max;
+	s64				sum_block_runtime;
+
 	u64				exec_max;
 	u64				slice_max;
 
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index d1bc616936d9..0995412dd3c0 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -499,10 +499,11 @@ print_task(struct seq_file *m, struct rq *rq, struct task_struct *p)
 		(long long)(p->nvcsw + p->nivcsw),
 		p->prio);
 
-	SEQ_printf(m, "%9Ld.%06ld %9Ld.%06ld %9Ld.%06ld",
+	SEQ_printf(m, "%9lld.%06ld %9lld.%06ld %9lld.%06ld %9lld.%06ld",
 		SPLIT_NS(schedstat_val_or_zero(p->stats.wait_sum)),
 		SPLIT_NS(p->se.sum_exec_runtime),
-		SPLIT_NS(schedstat_val_or_zero(p->stats.sum_sleep_runtime)));
+		SPLIT_NS(schedstat_val_or_zero(p->stats.sum_sleep_runtime)),
+		SPLIT_NS(schedstat_val_or_zero(p->stats.sum_block_runtime)));
 
 #ifdef CONFIG_NUMA_BALANCING
 	SEQ_printf(m, " %d %d", task_node(p), task_numa_group_id(p));
@@ -941,6 +942,7 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns,
 		u64 avg_atom, avg_per_cpu;
 
 		PN_SCHEDSTAT(stats.sum_sleep_runtime);
+		PN_SCHEDSTAT(stats.sum_block_runtime);
 		PN_SCHEDSTAT(stats.wait_start);
 		PN_SCHEDSTAT(stats.sleep_start);
 		PN_SCHEDSTAT(stats.block_start);
diff --git a/kernel/sched/stats.c b/kernel/sched/stats.c
index b2542f4d3192..21fae41c06f5 100644
--- a/kernel/sched/stats.c
+++ b/kernel/sched/stats.c
@@ -82,6 +82,7 @@ void __update_stats_enqueue_sleeper(struct rq *rq, struct task_struct *p,
 
 		__schedstat_set(stats->block_start, 0);
 		__schedstat_add(stats->sum_sleep_runtime, delta);
+		__schedstat_add(stats->sum_block_runtime, delta);
 
 		if (p) {
 			if (p->in_iowait) {
-- 
2.18.2