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linux-next/drivers/md/dm-stats.h
Mikulas Patocka fd2ed4d252 dm: add statistics support
Support the collection of I/O statistics on user-defined regions of
a DM device.  If no regions are defined no statistics are collected so
there isn't any performance impact.  Only bio-based DM devices are
currently supported.

Each user-defined region specifies a starting sector, length and step.
Individual statistics will be collected for each step-sized area within
the range specified.

The I/O statistics counters for each step-sized area of a region are
in the same format as /sys/block/*/stat or /proc/diskstats but extra
counters (12 and 13) are provided: total time spent reading and
writing in milliseconds.  All these counters may be accessed by sending
the @stats_print message to the appropriate DM device via dmsetup.

The creation of DM statistics will allocate memory via kmalloc or
fallback to using vmalloc space.  At most, 1/4 of the overall system
memory may be allocated by DM statistics.  The admin can see how much
memory is used by reading
/sys/module/dm_mod/parameters/stats_current_allocated_bytes

See Documentation/device-mapper/statistics.txt for more details.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2013-09-05 20:46:06 -04:00

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904 B
C

#ifndef DM_STATS_H
#define DM_STATS_H
#include <linux/types.h>
#include <linux/mutex.h>
#include <linux/list.h>
int dm_statistics_init(void);
void dm_statistics_exit(void);
struct dm_stats {
struct mutex mutex;
struct list_head list; /* list of struct dm_stat */
struct dm_stats_last_position __percpu *last;
sector_t last_sector;
unsigned last_rw;
};
struct dm_stats_aux {
bool merged;
};
void dm_stats_init(struct dm_stats *st);
void dm_stats_cleanup(struct dm_stats *st);
struct mapped_device;
int dm_stats_message(struct mapped_device *md, unsigned argc, char **argv,
char *result, unsigned maxlen);
void dm_stats_account_io(struct dm_stats *stats, unsigned long bi_rw,
sector_t bi_sector, unsigned bi_sectors, bool end,
unsigned long duration, struct dm_stats_aux *aux);
static inline bool dm_stats_used(struct dm_stats *st)
{
return !list_empty(&st->list);
}
#endif