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SubjectRe: [PATCH] tracing: simplify print_graph_cpu()
On Tue, Jul 28, 2009 at 08:26:06PM +0800, Lai Jiangshan wrote:
>
> print_graph_cpu() is little over-designed.
>
> And "log10_all" may be wrong when there are holes in cpu_online_mask:
> the max online cpu id > cpumask_weight(cpu_online_mask)
>
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
> diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> index abf7c4a..e30472d 100644
> --- a/kernel/trace/trace_functions_graph.c
> +++ b/kernel/trace/trace_functions_graph.c
> @@ -183,43 +183,19 @@ static void graph_trace_reset(struct trace_array *tr)
> unregister_ftrace_graph();
> }
>
> -static inline int log10_cpu(int nb)
> -{
> - if (nb / 100)
> - return 3;
> - if (nb / 10)
> - return 2;
> - return 1;
> -}
> +static int max_bytes_for_cpu;
>
> static enum print_line_t
> print_graph_cpu(struct trace_seq *s, int cpu)
> {
> - int i;
> int ret;
> - int log10_this = log10_cpu(cpu);
> - int log10_all = log10_cpu(cpumask_weight(cpu_online_mask));
> -
>
> /*
> * Start with a space character - to make it stand out
> * to the right a bit when trace output is pasted into
> * email:
> */
> - ret = trace_seq_printf(s, " ");
> -
> - /*
> - * Tricky - we space the CPU field according to the max
> - * number of online CPUs. On a 2-cpu system it would take
> - * a maximum of 1 digit - on a 128 cpu system it would
> - * take up to 3 digits:
> - */
> - for (i = 0; i < log10_all - log10_this; i++) {
> - ret = trace_seq_printf(s, " ");
> - if (!ret)
> - return TRACE_TYPE_PARTIAL_LINE;
> - }
> - ret = trace_seq_printf(s, "%d) ", cpu);
> + ret = trace_seq_printf(s, " %*d) ", max_bytes_for_cpu, cpu);
> if (!ret)
> return TRACE_TYPE_PARTIAL_LINE;
>
> @@ -919,6 +895,8 @@ static struct tracer graph_trace __read_mostly = {
>
> static __init int init_graph_trace(void)
> {
> + max_bytes_for_cpu = snprintf(NULL, 0, "%d", nr_cpu_ids - 1);


Nice trick :-)

Queued for .32, thanks!



> +
> return register_tracer(&graph_trace);
> }
>
>
>
>
>



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