Messages in this thread Patch in this message | | | Date | Fri, 21 Nov 2008 20:25:44 -0800 | From | Keika Kobayashi <> | Subject | [PATCH 1/3 v2] softirq: Introduce statistics for softirq |
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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> --- 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
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