On Tue, 26 Mar 2013 19:56:30 -0500 Nathan Zimmer <[email protected]> wrote:
> When running with 4096 cores attemping to read /proc/timer_list will fail
> with an ENOMEM condition. On a sufficantly large systems the total amount
> of data is more then 4mb, so it won't fit into a single buffer. The
> failure can also occur on smaller systems when memory fragmentation is
> high as reported by Dave Jones.
>
> Convert /proc/timer_list to a proper seq_file with its own iterator. This
> is a little more complex given that we have to make two passes with two
> separate headers.
>
> sysrq_timer_list_show also needed to be updated to reflect the fact that
> now timer_list_show only does one cpu at at time.
>
> ...
>
> --- a/kernel/time/timer_list.c
> +++ b/kernel/time/timer_list.c
> @@ -20,6 +20,13 @@
>
> #include <asm/uaccess.h>
>
> +
> +struct timer_list_iter {
> + int cpu;
> + bool second_pass;
> + u64 now;
> +};
> +
> typedef void (*print_fn_t)(struct seq_file *m, unsigned int *classes);
>
> DECLARE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases);
> @@ -247,43 +254,101 @@ static void timer_list_show_tickdevices_header(struct
> seq_file *m)
> }
> #endif
>
> -static int timer_list_show(struct seq_file *m, void *v)
> +static inline void timer_list_header(struct seq_file *m, u64 now)
There's really no point in the explicit inline directive - modern gcc's
basically ignore it anyway.
> {
> - u64 now = ktime_to_ns(ktime_get());
> - int cpu;
> -
> SEQ_printf(m, "Timer List Version: v0.7\n");
> SEQ_printf(m, "HRTIMER_MAX_CLOCK_BASES: %d\n", HRTIMER_MAX_CLOCK_BASES);
> SEQ_printf(m, "now at %Ld nsecs\n", (unsigned long long)now);
> SEQ_printf(m, "\n");
> +}
>
> ...
>
> +void sysrq_timer_list_show(void)
> +{
> + u64 now = ktime_to_ns(ktime_get());
> + int cpu;
> +
> + timer_list_header(NULL, now);
>
> for_each_online_cpu(cpu)
hm, it seems this code is taking the optimistic approach to CPU hotplug.
> - print_cpu(m, cpu, now);
> + print_cpu(NULL, cpu, now);
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