Re: [PATCH] Add num_to_str() for speedup /proc/stat

[Andrea Righi]

On Mon, Jan 30, 2012 at 02:16:19PM +0900, KAMEZAWA Hiroyuki wrote:
...
> diff --git a/fs/proc/stat.c b/fs/proc/stat.c
> index 121f77c..0ff3b92 100644
> --- a/fs/proc/stat.c
> +++ b/fs/proc/stat.c
> @@ -89,18 +89,19 @@ static int show_stat(struct seq_file *p, void *v)
>  	}
>  	sum += arch_irq_stat();
>  
> -	seq_printf(p, "cpu  %llu %llu %llu %llu %llu %llu %llu %llu %llu "
> -		"%llu\n",
> -		(unsigned long long)cputime64_to_clock_t(user),
> -		(unsigned long long)cputime64_to_clock_t(nice),
> -		(unsigned long long)cputime64_to_clock_t(system),
> -		(unsigned long long)cputime64_to_clock_t(idle),
> -		(unsigned long long)cputime64_to_clock_t(iowait),
> -		(unsigned long long)cputime64_to_clock_t(irq),
> -		(unsigned long long)cputime64_to_clock_t(softirq),
> -		(unsigned long long)cputime64_to_clock_t(steal),
> -		(unsigned long long)cputime64_to_clock_t(guest),
> -		(unsigned long long)cputime64_to_clock_t(guest_nice));
> +	seq_puts(p, "cpu ");
> +	seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(user));
> +	seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(nice));
> +	seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(system));
> +	seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(idle));
> +	seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(iowait));
> +	seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(irq));
> +	seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(softirq));
> +	seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(steal));
> +	seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(guest));
> +	seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(guest_nice));
> +	seq_putc(p, '\n');
> +
>  	for_each_online_cpu(i) {
>  		/* Copy values here to work around gcc-2.95.3, gcc-2.96 */
>  		user = kcpustat_cpu(i).cpustat[CPUTIME_USER];
> @@ -113,26 +114,24 @@ static int show_stat(struct seq_file *p, void *v)
>  		steal = kcpustat_cpu(i).cpustat[CPUTIME_STEAL];
>  		guest = kcpustat_cpu(i).cpustat[CPUTIME_GUEST];
>  		guest_nice = kcpustat_cpu(i).cpustat[CPUTIME_GUEST_NICE];
> -		seq_printf(p,
> -			"cpu%d %llu %llu %llu %llu %llu %llu %llu %llu %llu "
> -			"%llu\n",
> -			i,
> -			(unsigned long long)cputime64_to_clock_t(user),
> -			(unsigned long long)cputime64_to_clock_t(nice),
> -			(unsigned long long)cputime64_to_clock_t(system),
> -			(unsigned long long)cputime64_to_clock_t(idle),
> -			(unsigned long long)cputime64_to_clock_t(iowait),
> -			(unsigned long long)cputime64_to_clock_t(irq),
> -			(unsigned long long)cputime64_to_clock_t(softirq),
> -			(unsigned long long)cputime64_to_clock_t(steal),
> -			(unsigned long long)cputime64_to_clock_t(guest),
> -			(unsigned long long)cputime64_to_clock_t(guest_nice));
> +		seq_printf(p, "cpu %d", i);
                               ^^^^^^
mmh... if I'm not wrong this looks like an ABI change.

Thanks,
-Andrea

---
From: Andrea Righi <andrea@xxxxxxxxxxxxxxx>
Subject: procfs: avoid breaking the ABI in /proc/stat

The speed up of /proc/stat changed the output of the cpu statistics
adding an extra space between the string "cpu" and the cpu id.

Restore the old ABI by removing this space.

Signed-off-by: Andrea Righi <andrea@xxxxxxxxxxxxxxx>
---
 fs/proc/stat.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/proc/stat.c b/fs/proc/stat.c
index 0ff3b92..7ed7efa 100644
--- a/fs/proc/stat.c
+++ b/fs/proc/stat.c
@@ -114,7 +114,7 @@ static int show_stat(struct seq_file *p, void *v)
 		steal = kcpustat_cpu(i).cpustat[CPUTIME_STEAL];
 		guest = kcpustat_cpu(i).cpustat[CPUTIME_GUEST];
 		guest_nice = kcpustat_cpu(i).cpustat[CPUTIME_GUEST_NICE];
-		seq_printf(p, "cpu %d", i);
+		seq_printf(p, "cpu%d", i);
 		seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(user));
 		seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(nice));
 		seq_put_decimal_ull(p, ' ', cputime64_to_clock_t(system));

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