Re: [PATCH 2/3] proc: Export statistics for softirq to /proc

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 20 Nov 2008 19:58:43 -0800 Keika Kobayashi <kobayashi.kk@ncos.nec.co.jp> wrote:

> Export statistics for softirq in /proc/softirqs and /proc/stat.
> 
> 1. /proc/softirqs
> Implement /proc/softirqs which shows the number of softirq
> for each CPU like /proc/interrupts.
> 
> 2. /proc/stat
> Add the "softirq" line to /proc/stat.
> This line shows the number of softirq for all cpu.
> The first column is the total of all softirqs and
> each subsequent column is the total for particular softirq.
> 
> Signed-off-by: Keika Kobayashi <kobayashi.kk@ncos.nec.co.jp>
> Reviewed-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>

This all looks reasonable to me.

>  fs/proc/Makefile          |    1 +
>  fs/proc/softirqs.c        |   57 +++++++++++++++++++++++++++++++++++++++++++++
>  fs/proc/stat.c            |   17 +++++++++++++
>  include/linux/interrupt.h |    3 ++
>  4 files changed, 78 insertions(+), 0 deletions(-)
>  create mode 100644 fs/proc/softirqs.c
> 
> diff --git a/fs/proc/Makefile b/fs/proc/Makefile
> index 63d9651..11a7b5c 100644
> --- a/fs/proc/Makefile
> +++ b/fs/proc/Makefile
> @@ -18,6 +18,7 @@ proc-y	+= meminfo.o
>  proc-y	+= stat.o
>  proc-y	+= uptime.o
>  proc-y	+= version.o
> +proc-y	+= softirqs.o
>  proc-$(CONFIG_PROC_SYSCTL)	+= proc_sysctl.o
>  proc-$(CONFIG_NET)		+= proc_net.o
>  proc-$(CONFIG_PROC_KCORE)	+= kcore.o
> diff --git a/fs/proc/softirqs.c b/fs/proc/softirqs.c
> new file mode 100644
> index 0000000..43d3bc0
> --- /dev/null
> +++ b/fs/proc/softirqs.c
> @@ -0,0 +1,57 @@
> +#include <linux/init.h>
> +#include <linux/kernel_stat.h>
> +#include <linux/proc_fs.h>
> +#include <linux/seq_file.h>
> +
> +static const char *desc_array[] = {
> +	"HI",
> +	"TIMER",
> +	"NET_TX",
> +	"NET_RX",
> +	"BLOCK",
> +	"TASKLET",
> +	"SCHED",
> +#ifdef CONFIG_HIGH_RES_TIMERS
> +	"HRTIMER",
> +#endif
> +	"RCU"};
> +
> +/*
> + * /proc/softirqs  ... display the number of softirqs
> + */
> +static int show_softirqs(struct seq_file *p, void *v)
> +{
> +	int i, j;
> +
> +	seq_printf(p, "                ");
> +	for_each_online_cpu(i)
> +		seq_printf(p, "CPU%-8d", i);
> +	seq_printf(p, "\n");
> +
> +	for_each_softirq_nr(i) {
> +		seq_printf(p, "%-10s", desc_array[i]);
> +		for_each_online_cpu(j)
> +			seq_printf(p, "%10u ", kstat_softirqs_cpu(i, j));
> +		seq_printf(p, "\n");
> +	}
> +	return 0;
> +}

This uses for_each_online_cpu(), but below we use for_each_possible_cpu().

Shouldn't we be consistent here so that at least the numbers will add
up to the same thing?

Probably for_each_possible_cpu() is best - people might want to see how
many softirqs happened on a CPU which was recently offlined.

> +
> +static int softirqs_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, show_softirqs, NULL);
> +}
> +
> +static struct file_operations proc_softirqs_operations = {

Make this const, please.

> +	.open		= softirqs_open,
> +	.read		= seq_read,
> +	.llseek		= seq_lseek,
> +	.release	= single_release,
> +};
> +
> +static int __init proc_softirqs_init(void)
> +{
> +	proc_create("softirqs", 0, NULL, &proc_softirqs_operations);
> +	return 0;
> +}
> +module_init(proc_softirqs_init);
> diff --git a/fs/proc/stat.c b/fs/proc/stat.c
> index 81904f0..02d5bf8 100644
> --- a/fs/proc/stat.c
> +++ b/fs/proc/stat.c
> @@ -25,6 +25,7 @@ static int show_stat(struct seq_file *p, void *v)
>  	cputime64_t user, nice, system, idle, iowait, irq, softirq, steal;
>  	cputime64_t guest;
>  	u64 sum = 0;
> +	u64 sum_softirq = 0;
>  	struct timespec boottime;
>  	unsigned int per_irq_sum;
>  
> @@ -49,6 +50,10 @@ static int show_stat(struct seq_file *p, void *v)
>  			sum += kstat_irqs_cpu(j, i);
>  
>  		sum += arch_irq_stat_cpu(i);
> +
> +		for_each_softirq_nr(j)
> +			sum_softirq += kstat_softirqs_cpu(j, i);
> +
>  	}
>  	sum += arch_irq_stat();
>  
> @@ -111,6 +116,18 @@ static int show_stat(struct seq_file *p, void *v)
>  		nr_running(),
>  		nr_iowait());
>  
> +	seq_printf(p, "softirq %llu", (unsigned long long)sum_softirq);
> +
> +	for_each_softirq_nr(i) {
> +		per_irq_sum = 0;
> +
> +		for_each_possible_cpu(j)
> +			per_irq_sum += kstat_softirqs_cpu(i, j);
> +
> +		seq_printf(p, " %u", per_irq_sum);
> +	}
> +	seq_printf(p, "\n");
> +
>  	return 0;
>  }
>  
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index f58a0cf..9a12ba0 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -259,6 +259,9 @@ enum
>  	NR_SOFTIRQS
>  };
>  
> +#define for_each_softirq_nr(irq)		\
> +	for (irq = 0; irq < NR_SOFTIRQS; irq++)

Can we remove this please?  It doesn't make the code any more readable.
Just open-code the loop at each site.

(And strictly speaking the `irq' macro arg should be parenthesised)