Subject: [PATCH 1/3] softirq: Introduce statistics for softirq
Newsgroups: gmane.linux.kernel
Date: 2008-11-21 03:55:42 GMT (3 years, 25 weeks, 6 days, 10 hours and 21 minutes ago)
Statistics for softirq doesn't exist.
It will be helpful like statistics for interrupts.
This patch introduces counting the number of softirq,
which will be exported in /proc/softirqs.
When softirq handler consumes much CPU time,
/proc/stat is like the following.
$ while :; do cat /proc/stat | head -n1 ; sleep 10 ; done
cpu 88 0 408 739665 583 28 2 0 0
cpu 450 0 1090 740970 594 28 1294 0 0
^^^^
softirq
In such a situation,
/proc/softirqs shows us which softirq handler is invoked.
We can see the increase rate of softirqs.
<before>
$ cat /proc/softirqs
CPU0 CPU1 CPU2 CPU3
HI 0 0 0 0
TIMER 462850 462805 462782 462718
NET_TX 0 0 0 365
NET_RX 2472 2 2 40
BLOCK 0 0 381 1164
TASKLET 0 0 0 224
SCHED 462654 462689 462698 462427
RCU 3046 2423 3367 3173
<after>
$ cat /proc/softirqs
CPU0 CPU1 CPU2 CPU3
HI 0 0 0 0
TIMER 463361 465077 465056 464991
NET_TX 53 0 1 365
NET_RX 3757 2 2 40
BLOCK 0 0 398 1170
TASKLET 0 0 0 224
SCHED 463074 464318 464612 463330
RCU 3505 2948 3947 3673
When CPU TIME of softirq is high,
the rates of increase is the following.
TIMER : 220/sec : CPU1-3
NET_TX : 5/sec : CPU0
NET_RX : 120/sec : CPU0
SCHED : 40-200/sec : all CPU
RCU : 45-58/sec : all CPU
The rates of increase in an idle mode is the following.
TIMER : 250/sec
SCHED : 250/sec
RCU : 2/sec
It seems many softirqs for receiving packets and rcu are invoked.
This gives us help for checking system.
Signed-off-by: Keika Kobayashi <kobayashi.kk <at> ncos.nec.co.jp>
Reviewed-by: Hiroshi Shimamoto <h-shimamoto <at> ct.jp.nec.com>
---
include/linux/kernel_stat.h | 12 ++++++++++++
kernel/softirq.c | 1 +
2 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h
index 4a145ca..57c1643 100644
--- a/include/linux/kernel_stat.h
+++ b/include/linux/kernel_stat.h
@@ -5,6 +5,7 @@
#include <linux/threads.h>
#include <linux/percpu.h>
#include <linux/cpumask.h>
+#include <linux/interrupt.h>
#include <asm/irq.h>
#include <asm/cputime.h>
@@ -29,6 +30,7 @@ struct cpu_usage_stat {
struct kernel_stat {
struct cpu_usage_stat cpustat;
unsigned int irqs[NR_IRQS];
+ unsigned int softirqs[NR_SOFTIRQS];
};
DECLARE_PER_CPU(struct kernel_stat, kstat);
@@ -52,6 +54,16 @@ static inline unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
return kstat_cpu(cpu).irqs[irq];
}
+static inline void kstat_incr_softirqs_this_cpu(unsigned int irq)
+{
+ kstat_this_cpu.softirqs[irq]++;
+}
+
+static inline unsigned int kstat_softirqs_cpu(unsigned int irq, int cpu)
+{
+ return kstat_cpu(cpu).softirqs[irq];
+}
+
/*
* Number of interrupts per specific IRQ source, since bootup
*/
diff --git a/kernel/softirq.c b/kernel/softirq.c
index e7c69a7..088e179 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -208,6 +208,7 @@ restart:
do {
if (pending & 1) {
int prev_count = preempt_count();
+ kstat_incr_softirqs_this_cpu(h - softirq_vec);
h->action(h);
--
1.5.0.6