On Tue, Jun 09 2015 at 5:21pm -0400,
Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote:
> This patch makes it possible to use precise timestamps with nanosecond
> granularity in dm statistics.
>
> Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
>
> ---
> Documentation/device-mapper/statistics.txt | 25 ++++-
> drivers/md/dm-stats.c | 139 +++++++++++++++++++++--------
> drivers/md/dm-stats.h | 4
> 3 files changed, 125 insertions(+), 43 deletions(-)
>
> Index: linux-4.1-rc7/drivers/md/dm-stats.c
> ===================================================================
> --- linux-4.1-rc7.orig/drivers/md/dm-stats.c 2015-06-08 16:02:27.000000000 +0200
> +++ linux-4.1-rc7/drivers/md/dm-stats.c 2015-06-08 16:38:43.000000000 +0200
> @@ -33,13 +33,14 @@ struct dm_stat_percpu {
>
> struct dm_stat_shared {
> atomic_t in_flight[2];
> - unsigned long stamp;
> + unsigned long long stamp;
> struct dm_stat_percpu tmp;
> };
>
> struct dm_stat {
> struct list_head list_entry;
> int id;
> + unsigned stat_flags;
> size_t n_entries;
> sector_t start;
> sector_t end;
> @@ -53,6 +54,8 @@ struct dm_stat {
> struct dm_stat_shared stat_shared[0];
> };
>
> +#define STAT_PRECISE_TIMESTAMPS 1
> +
> struct dm_stats_last_position {
> sector_t last_sector;
> unsigned last_rw;
> @@ -227,7 +230,8 @@ void dm_stats_cleanup(struct dm_stats *s
> }
>
> static int dm_stats_create(struct dm_stats *stats, sector_t start, sector_t end,
> - sector_t step, const char *program_id, const char *aux_data,
> + sector_t step, unsigned stat_flags,
> + const char *program_id, const char *aux_data,
> void (*suspend_callback)(struct mapped_device *),
> void (*resume_callback)(struct mapped_device *),
> struct mapped_device *md)
> @@ -268,6 +272,7 @@ static int dm_stats_create(struct dm_sta
> if (!s)
> return -ENOMEM;
>
> + s->stat_flags = stat_flags;
> s->n_entries = n_entries;
> s->start = start;
> s->end = end;
> @@ -417,15 +422,22 @@ static int dm_stats_list(struct dm_stats
> return 1;
> }
>
> -static void dm_stat_round(struct dm_stat_shared *shared, struct dm_stat_percpu *p)
> +static void dm_stat_round(struct dm_stat *s, struct dm_stat_shared *shared,
> + struct dm_stat_percpu *p)
> {
> /*
> * This is racy, but so is part_round_stats_single.
> */
> - unsigned long now = jiffies;
> - unsigned in_flight_read;
> - unsigned in_flight_write;
> - unsigned long difference = now - shared->stamp;
> + unsigned long long now, difference;
> + unsigned in_flight_read, in_flight_write;
> +
> + if (likely(!(s->stat_flags & STAT_PRECISE_TIMESTAMPS))) {
> + now = jiffies;
> + } else {
> + now = ktime_to_ns(ktime_get());
> + }
> +
> + difference = now - shared->stamp;
>
> if (!difference)
> return;
Here 'difference' is in nanosecond resolution if STAT_PRECISE_TIMESTAMPS
> @@ -646,11 +673,15 @@ static int dm_stats_clear(struct dm_stat
> /*
> * This is like jiffies_to_msec, but works for 64-bit values.
> */
> -static unsigned long long dm_jiffies_to_msec64(unsigned long long j)
> +static unsigned long long dm_jiffies_to_msec64(struct dm_stat *s, unsigned long long j)
> {
> - unsigned long long result = 0;
> + unsigned long long result;
> unsigned mult;
>
> + if (s->stat_flags & STAT_PRECISE_TIMESTAMPS)
> + return j;
> +
> + result = 0;
> if (j)
> result = jiffies_to_msecs(j & 0x3fffff);
> if (j >= 1 << 22) {
Yet here you aren't converting ns to ms...
> @@ -712,16 +743,16 @@ static int dm_stats_print(struct dm_stat
> shared->tmp.ios[READ],
> shared->tmp.merges[READ],
> shared->tmp.sectors[READ],
> - dm_jiffies_to_msec64(shared->tmp.ticks[READ]),
> + dm_jiffies_to_msec64(s, shared->tmp.ticks[READ]),
> shared->tmp.ios[WRITE],
> shared->tmp.merges[WRITE],
> shared->tmp.sectors[WRITE],
> - dm_jiffies_to_msec64(shared->tmp.ticks[WRITE]),
> + dm_jiffies_to_msec64(s, shared->tmp.ticks[WRITE]),
> dm_stat_in_flight(shared),
> - dm_jiffies_to_msec64(shared->tmp.io_ticks_total),
> - dm_jiffies_to_msec64(shared->tmp.time_in_queue),
> - dm_jiffies_to_msec64(shared->tmp.io_ticks[READ]),
> - dm_jiffies_to_msec64(shared->tmp.io_ticks[WRITE]));
> + dm_jiffies_to_msec64(s, shared->tmp.io_ticks_total),
> + 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 (unlikely(sz + 1 >= maxlen))
> goto buffer_overflow;
So the printed stats won't actually be in msec.
Or am I missing something?
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