[dm-devel] [PATCH 3/4] dm stats: report histogram of latencies

[Coly Li]

在 15/6/10 上午5:22, Mikulas Patocka 写道:
> This patch adds an option to dm statistics to collect and report the
> histogram of latencies.
>
> Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
>
> ---
>  Documentation/device-mapper/statistics.txt |   21 ++-
>  drivers/md/dm-stats.c                      |  201 +++++++++++++++++++++++++----
>  2 files changed, 196 insertions(+), 26 deletions(-)
>
> Index: linux-4.1-rc7/drivers/md/dm-stats.c
> ===================================================================
> --- linux-4.1-rc7.orig/drivers/md/dm-stats.c	2015-06-08 16:38:43.000000000 +0200
> +++ linux-4.1-rc7/drivers/md/dm-stats.c	2015-06-08 17:02:01.000000000 +0200
> @@ -29,6 +29,7 @@ struct dm_stat_percpu {
>  	unsigned long long io_ticks[2];
>  	unsigned long long io_ticks_total;
>  	unsigned long long time_in_queue;
> +	unsigned long long *histogram;
>  };
>  
>  struct dm_stat_shared {
[snip]
> @@ -619,6 +700,11 @@ static void __dm_stat_init_temporary_per
>  		shared->tmp.io_ticks[WRITE] += ACCESS_ONCE(p->io_ticks[WRITE]);
>  		shared->tmp.io_ticks_total += ACCESS_ONCE(p->io_ticks_total);
>  		shared->tmp.time_in_queue += ACCESS_ONCE(p->time_in_queue);
> +		if (s->n_histogram_entries) {
> +			unsigned i;
> +			for (i = 0; i < s->n_histogram_entries + 1; i++)
> +				shared->tmp.histogram[i] += ACCESS_ONCE(p->histogram[i]);

s->n_histogram_entries + 1 in for() looping will be calculated many times, maybe this way could be better,

+		if (s->n_histogram_entries) {
+			unsigned i, j;
+			j = s->n_histogram_entries + 1;
+			for (i = 0; i < j; i++)
+				shared->tmp.histogram[i] += ACCESS_ONCE(p->histogram[i]);

> +		}
>  	}
>  }
>  
> @@ -648,6 +734,15 @@ static void __dm_stat_clear(struct dm_st
>  		p->io_ticks_total -= shared->tmp.io_ticks_total;
>  		p->time_in_queue -= shared->tmp.time_in_queue;
>  		local_irq_enable();
> +		if (s->n_histogram_entries) {
> +			unsigned i;
> +			for (i = 0; i < s->n_histogram_entries + 1; i++) {
Same situation here,

+            unsigned i, j;
+            j = s->n_histogram_entries + 1;
+            for (i = 0; i < j; i++) {

> +				local_irq_disable();
> +				p = &s->stat_percpu[smp_processor_id()][x];
> +				p->histogram[i] -= shared->tmp.histogram[i];
> +				local_irq_enable();
> +			}
> +		}
>  	}
>  }
>  
> @@ -737,7 +832,7 @@ static int dm_stats_print(struct dm_stat
>  
>  		__dm_stat_init_temporary_percpu_totals(shared, s, x);
>  
> -		DMEMIT("%llu+%llu %llu %llu %llu %llu %llu %llu %llu %llu %d %llu %llu %llu %llu\n",
> +		DMEMIT("%llu+%llu %llu %llu %llu %llu %llu %llu %llu %llu %d %llu %llu %llu %llu",
>  		       (unsigned long long)start,
>  		       (unsigned long long)step,
>  		       shared->tmp.ios[READ],
> @@ -753,6 +848,13 @@ static int dm_stats_print(struct dm_stat
>  		       dm_jiffies_to_msec64(s, shared->tmp.time_in_queue),
>  		       dm_jiffies_to_msec64(s, shared->tmp.io_ticks[READ]),
>  		       dm_jiffies_to_msec64(s, shared->tmp.io_ticks[WRITE]));
> +		if (s->n_histogram_entries) {
> +			unsigned i;
> +			for (i = 0; i < s->n_histogram_entries + 1; i++) {
Same situation here,

+                        unsigned i, j;
+                        j = s->n_histogram_entries + 1;
+                        for (i = 0; i < j; i++) {

> +				DMEMIT("%s%llu", !i ? " " : ":", shared->tmp.histogram[i]);
> +			}
> +		}
> +		DMEMIT("\n");
>  
>  		if (unlikely(sz + 1 >= maxlen))
>  			goto buffer_overflow;
[snip]

Coly