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