linux-kernel - [PATCH v2 3/6] sched: Report the different kinds of imbalances in /proc/schedstat

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Message-ID: <20241220063224.17767-4-swapnil.sapkal@amd.com>
Date: Fri, 20 Dec 2024 06:32:21 +0000
From: Swapnil Sapkal <swapnil.sapkal@....com>
To: <peterz@...radead.org>, <mingo@...hat.com>, <juri.lelli@...hat.com>,
	<vincent.guittot@...aro.org>, <corbet@....net>
CC: <dietmar.eggemann@....com>, <rostedt@...dmis.org>, <bsegall@...gle.com>,
	<mgorman@...e.de>, <vschneid@...hat.com>, <iamjoonsoo.kim@....com>,
	<qyousef@...alina.io>, <sshegde@...ux.ibm.com>, <alexs@...nel.org>,
	<lukasz.luba@....com>, <gautham.shenoy@....com>, <kprateek.nayak@....com>,
	<ravi.bangoria@....com>, <swapnil.sapkal@....com>,
	<linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>
Subject: [PATCH v2 3/6] sched: Report the different kinds of imbalances in /proc/schedstat

In /proc/schedstat, lb_imbalance reports the sum of imbalances
discovered in sched domains with each call to sched_balance_rq(), which is
not very useful because lb_imbalance does not mention whether the imbalance
is due to load, utilization, nr_tasks or misfit_tasks. Remove this field
from /proc/schedstat.

Currently there is no field in /proc/schedstat to report different types
of imbalances. Introduce new fields in /proc/schedstat to report the
total imbalances in load, utilization, nr_tasks or misfit_tasks.

Added fields to /proc/schedstat:
        - lb_imbalance_load: Total imbalance due to load.
        - lb_imbalance_util: Total imbalance due to utilization.
        - lb_imbalance_task: Total imbalance due to number of tasks.
        - lb_imbalance_misfit: Total imbalance due to misfit tasks.

Reviewed-by: Shrikanth Hegde <sshegde@...ux.ibm.com>
Signed-off-by: Swapnil Sapkal <swapnil.sapkal@....com>
---
 include/linux/sched/topology.h |  5 ++++-
 kernel/sched/fair.c            | 24 +++++++++++++++++++++++-
 kernel/sched/stats.c           |  7 +++++--
 3 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index 4237daa5ac7a..76a662e1ec24 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -114,7 +114,10 @@ struct sched_domain {
 	unsigned int lb_count[CPU_MAX_IDLE_TYPES];
 	unsigned int lb_failed[CPU_MAX_IDLE_TYPES];
 	unsigned int lb_balanced[CPU_MAX_IDLE_TYPES];
-	unsigned int lb_imbalance[CPU_MAX_IDLE_TYPES];
+	unsigned int lb_imbalance_load[CPU_MAX_IDLE_TYPES];
+	unsigned int lb_imbalance_util[CPU_MAX_IDLE_TYPES];
+	unsigned int lb_imbalance_task[CPU_MAX_IDLE_TYPES];
+	unsigned int lb_imbalance_misfit[CPU_MAX_IDLE_TYPES];
 	unsigned int lb_gained[CPU_MAX_IDLE_TYPES];
 	unsigned int lb_hot_gained[CPU_MAX_IDLE_TYPES];
 	unsigned int lb_nobusyg[CPU_MAX_IDLE_TYPES];
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2ca3f098552c..5e7e4fe81648 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -11699,6 +11699,28 @@ static int should_we_balance(struct lb_env *env)
 	return group_balance_cpu(sg) == env->dst_cpu;
 }
 
+static void update_lb_imbalance_stat(struct lb_env *env, struct sched_domain *sd,
+				     enum cpu_idle_type idle)
+{
+	if (!schedstat_enabled())
+		return;
+
+	switch (env->migration_type) {
+	case migrate_load:
+		__schedstat_add(sd->lb_imbalance_load[idle], env->imbalance);
+		break;
+	case migrate_util:
+		__schedstat_add(sd->lb_imbalance_util[idle], env->imbalance);
+		break;
+	case migrate_task:
+		__schedstat_add(sd->lb_imbalance_task[idle], env->imbalance);
+		break;
+	case migrate_misfit:
+		__schedstat_add(sd->lb_imbalance_misfit[idle], env->imbalance);
+		break;
+	}
+}
+
 /*
  * Check this_cpu to ensure it is balanced within domain. Attempt to move
  * tasks if there is an imbalance.
@@ -11749,7 +11771,7 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq,
 
 	WARN_ON_ONCE(busiest == env.dst_rq);
 
-	schedstat_add(sd->lb_imbalance[idle], env.imbalance);
+	update_lb_imbalance_stat(&env, sd, idle);
 
 	env.src_cpu = busiest->cpu;
 	env.src_rq = busiest;
diff --git a/kernel/sched/stats.c b/kernel/sched/stats.c
index eb0cdcd4d921..802bd9398a2e 100644
--- a/kernel/sched/stats.c
+++ b/kernel/sched/stats.c
@@ -141,11 +141,14 @@ static int show_schedstat(struct seq_file *seq, void *v)
 			seq_printf(seq, "domain%d %*pb", dcount++,
 				   cpumask_pr_args(sched_domain_span(sd)));
 			for (itype = 0; itype < CPU_MAX_IDLE_TYPES; itype++) {
-				seq_printf(seq, " %u %u %u %u %u %u %u %u",
+				seq_printf(seq, " %u %u %u %u %u %u %u %u %u %u %u",
 				    sd->lb_count[itype],
 				    sd->lb_balanced[itype],
 				    sd->lb_failed[itype],
-				    sd->lb_imbalance[itype],
+				    sd->lb_imbalance_load[itype],
+				    sd->lb_imbalance_util[itype],
+				    sd->lb_imbalance_task[itype],
+				    sd->lb_imbalance_misfit[itype],
 				    sd->lb_gained[itype],
 				    sd->lb_hot_gained[itype],
 				    sd->lb_nobusyq[itype],
-- 
2.43.0