Techwizz/kernel-fxtec-pro1x
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

softirq: introduce statistics for softirq

Browse source 
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@ncos.nec.co.jp>
Reviewed-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Keika Kobayashi 2009-06-17 16:25:52 -07:00 committed by Linus Torvalds
parent 1d89b30cc9
commit aa0ce5bbc2
2 changed files with 13 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

12
include/linux/kernel_stat.h
View file

@ -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>
@ -31,6 +32,7 @@ struct kernel_stat {
#ifndef CONFIG_GENERIC_HARDIRQS
unsigned int irqs[NR_IRQS];
#endif
unsigned int softirqs[NR_SOFTIRQS];
};
DECLARE_PER_CPU(struct kernel_stat, kstat);
@ -67,6 +69,16 @@ extern unsigned int kstat_irqs_cpu(unsigned int irq, int cpu);
#endif
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
*/

1
kernel/softirq.c
View file

@ -213,6 +213,7 @@ asmlinkage void __do_softirq(void)
do {
if (pending & 1) {
int prev_count = preempt_count();
kstat_incr_softirqs_this_cpu(h - softirq_vec);
trace_softirq_entry(h, softirq_vec);
h->action(h);