Re: [RFC PATCH 4/7] core/metricfs: expose softirq information through metricfs

Add metricfs support for displaying percpu softirq counters.  The
top directory is /sys/kernel/debug/metricfs/softirq.  Then there
is a subdirectory for each softirq type.  For example:

    cat /sys/kernel/debug/metricfs/softirq/NET_RX/values

Signed-off-by: Jonathan Adams <redacted>

---

jwadams@google.com: rebased to 5.8-pre6
	This is work originally done by another engineer at
	google, who would rather not have their name associated with this
	patchset. They're okay with me sending it under my name.
---
 kernel/softirq.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index c4201b7f42b1..1ae3a540b789 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c

@@ -25,6 +25,8 @@
 #include <linux/smpboot.h>
 #include <linux/tick.h>
 #include <linux/irq.h>
+#include <linux/jump_label.h>
+#include <linux/metricfs.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/irq.h>

@@ -738,3 +740,46 @@ unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
 {
 	return from;
 }
+
+#ifdef CONFIG_METRICFS
+
+#define METRICFS_ITEM(name) \
+static void \
+metricfs_##name(struct metric_emitter *e, int cpu) \
+{ \
+	int64_t v = kstat_softirqs_cpu(name##_SOFTIRQ, cpu); \
+	METRIC_EMIT_PERCPU_INT(e, cpu, v); \
+} \
+METRIC_EXPORT_PERCPU_COUNTER(name, #name " softirq", metricfs_##name)
+
+METRICFS_ITEM(HI);
+METRICFS_ITEM(TIMER);
+METRICFS_ITEM(NET_TX);
+METRICFS_ITEM(NET_RX);
+METRICFS_ITEM(BLOCK);
+METRICFS_ITEM(IRQ_POLL);
+METRICFS_ITEM(TASKLET);
+METRICFS_ITEM(SCHED);
+METRICFS_ITEM(HRTIMER);
+METRICFS_ITEM(RCU);
+
+static int __init init_softirq_metricfs(void)
+{
+	struct metricfs_subsys *subsys;
+
+	subsys = metricfs_create_subsys("softirq", NULL);
+	metric_init_HI(subsys);
+	metric_init_TIMER(subsys);
+	metric_init_NET_TX(subsys);
+	metric_init_NET_RX(subsys);
+	metric_init_BLOCK(subsys);
+	metric_init_IRQ_POLL(subsys);
+	metric_init_TASKLET(subsys);
+	metric_init_SCHED(subsys);
+	metric_init_RCU(subsys);
+
+	return 0;
+}
+module_init(init_softirq_metricfs);