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dm writecache: add event counters 

Add 10 counters for various events (hit, miss, etc) and export them in
the status line (accessed from userspace with "dmsetup status"). Also
add a message "clear_stats" that resets these counters.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mikulas Patocka 2021-07-27 09:42:21 -04:00 committed by Mike Snitzer
parent df699cc16e
commit e3a35d0340
2 changed files with 67 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
Documentation/admin-guide/device-mapper/writecache.rst
View File

@ -78,13 +78,23 @@ Status:
2. the number of blocks
3. the number of free blocks
4. the number of blocks under writeback
5. the number of read requests
6. the number of read requests that hit the cache
7. the number of write requests
8. the number of write requests that hit uncommitted block
9. the number of write requests that hit committed block
10. the number of write requests that bypass the cache
11. the number of write requests that are allocated in the cache
12. the number of write requests that are blocked on the freelist
13. the number of flush requests
14. the number of discard requests
Messages:
flush
flush the cache device. The message returns successfully
Flush the cache device. The message returns successfully
if the cache device was flushed without an error
flush_on_suspend
flush the cache device on next suspend. Use this message
Flush the cache device on next suspend. Use this message
when you are going to remove the cache device. The proper
sequence for removing the cache device is:
@ -98,3 +108,5 @@ Messages:
6. the cache device is now inactive and it can be deleted
cleaner
See above "cleaner" constructor documentation.
clear_stats
Clear the statistics that are reported on the status line

56
drivers/md/dm-writecache.c
View File

@ -206,6 +206,19 @@ struct dm_writecache {
struct bio_set bio_set;
mempool_t copy_pool;
struct {
unsigned long long reads;
unsigned long long read_hits;
unsigned long long writes;
unsigned long long write_hits_uncommitted;
unsigned long long write_hits_committed;
unsigned long long writes_around;
unsigned long long writes_allocate;
unsigned long long writes_blocked_on_freelist;
unsigned long long flushes;
unsigned long long discards;
} stats;
};
#define WB_LIST_INLINE 16
@ -1157,6 +1170,18 @@ static int process_cleaner_mesg(unsigned argc, char **argv, struct dm_writecache
return 0;
}
static int process_clear_stats_mesg(unsigned argc, char **argv, struct dm_writecache *wc)
{
if (argc != 1)
return -EINVAL;
wc_lock(wc);
memset(&wc->stats, 0, sizeof wc->stats);
wc_unlock(wc);
return 0;
}
static int writecache_message(struct dm_target *ti, unsigned argc, char **argv,
char *result, unsigned maxlen)
{
@ -1169,6 +1194,8 @@ static int writecache_message(struct dm_target *ti, unsigned argc, char **argv,
r = process_flush_on_suspend_mesg(argc, argv, wc);
else if (!strcasecmp(argv[0], "cleaner"))
r = process_cleaner_mesg(argc, argv, wc);
else if (!strcasecmp(argv[0], "clear_stats"))
r = process_clear_stats_mesg(argc, argv, wc);
else
DMERR("unrecognised message received: %s", argv[0]);
@ -1320,8 +1347,10 @@ static enum wc_map_op writecache_map_read(struct dm_writecache *wc, struct bio *
struct wc_entry *e;
read_next_block:
wc->stats.reads++;
e = writecache_find_entry(wc, bio->bi_iter.bi_sector, WFE_RETURN_FOLLOWING);
if (e && read_original_sector(wc, e) == bio->bi_iter.bi_sector) {
wc->stats.read_hits++;
if (WC_MODE_PMEM(wc)) {
bio_copy_block(wc, bio, memory_data(wc, e));
if (bio->bi_iter.bi_size)
@ -1400,14 +1429,17 @@ static enum wc_map_op writecache_map_write(struct dm_writecache *wc, struct bio
do {
bool found_entry = false;
bool search_used = false;
wc->stats.writes++;
if (writecache_has_error(wc))
return WC_MAP_ERROR;
e = writecache_find_entry(wc, bio->bi_iter.bi_sector, 0);
if (e) {
if (!writecache_entry_is_committed(wc, e)) {
wc->stats.write_hits_uncommitted++;
search_used = true;
goto bio_copy;
}
wc->stats.write_hits_committed++;
if (!WC_MODE_PMEM(wc) && !e->write_in_progress) {
wc->overwrote_committed = true;
search_used = true;
@ -1423,15 +1455,18 @@ static enum wc_map_op writecache_map_write(struct dm_writecache *wc, struct bio
if (unlikely(!e)) {
if (!WC_MODE_PMEM(wc) && !found_entry) {
direct_write:
wc->stats.writes_around++;
e = writecache_find_entry(wc, bio->bi_iter.bi_sector, WFE_RETURN_FOLLOWING);
return writecache_map_remap_origin(wc, bio, e);
}
wc->stats.writes_blocked_on_freelist++;
writecache_wait_on_freelist(wc);
continue;
}
write_original_sector_seq_count(wc, e, bio->bi_iter.bi_sector, wc->seq_count);
writecache_insert_entry(wc, e);
wc->uncommitted_blocks++;
wc->stats.writes_allocate++;
bio_copy:
if (WC_MODE_PMEM(wc))
bio_copy_block(wc, bio, memory_data(wc, e));
@ -1453,6 +1488,7 @@ static enum wc_map_op writecache_map_flush(struct dm_writecache *wc, struct bio
return WC_MAP_ERROR;
if (WC_MODE_PMEM(wc)) {
wc->stats.flushes++;
writecache_flush(wc);
if (writecache_has_error(wc))
return WC_MAP_ERROR;
@ -1463,12 +1499,15 @@ static enum wc_map_op writecache_map_flush(struct dm_writecache *wc, struct bio
/* SSD: */
if (dm_bio_get_target_bio_nr(bio))
return WC_MAP_REMAP_ORIGIN;
wc->stats.flushes++;
writecache_offload_bio(wc, bio);
return WC_MAP_RETURN;
}
static enum wc_map_op writecache_map_discard(struct dm_writecache *wc, struct bio *bio)
{
wc->stats.discards++;
if (writecache_has_error(wc))
return WC_MAP_ERROR;
@ -2618,9 +2657,20 @@ static void writecache_status(struct dm_target *ti, status_type_t type,
switch (type) {
case STATUSTYPE_INFO:
DMEMIT("%ld %llu %llu %llu", writecache_has_error(wc),
DMEMIT("%ld %llu %llu %llu %llu %llu %llu %llu %llu %llu %llu %llu %llu %llu",
writecache_has_error(wc),
(unsigned long long)wc->n_blocks, (unsigned long long)wc->freelist_size,
(unsigned long long)wc->writeback_size);
(unsigned long long)wc->writeback_size,
wc->stats.reads,
wc->stats.read_hits,
wc->stats.writes,
wc->stats.write_hits_uncommitted,
wc->stats.write_hits_committed,
wc->stats.writes_around,
wc->stats.writes_allocate,
wc->stats.writes_blocked_on_freelist,
wc->stats.flushes,
wc->stats.discards);
break;
case STATUSTYPE_TABLE:
DMEMIT("%c %s %s %u ", WC_MODE_PMEM(wc) ? 'p' : 's',
@ -2678,7 +2728,7 @@ static void writecache_status(struct dm_target *ti, status_type_t type,
static struct target_type writecache_target = {
.name = "writecache",
.version = {1, 5, 0},
.version = {1, 6, 0},
.module = THIS_MODULE,
.ctr = writecache_ctr,
.dtr = writecache_dtr,