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    SubjectRe: [PATCH] Add num_to_str() for speedup /proc/stat
    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@betterlinux.com>
    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@betterlinux.com>
    ---
    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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