dm space map disk: cache a small number of index entries
The disk space map stores it's index entries in a btree, these are
accessed very frequently, so having a few cached makes a big difference
to performance.
With this change provisioning a new block takes roughly 20% less cpu.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/persistent-data/dm-space-map-common.c b/drivers/md/persistent-data/dm-space-map-common.c
index 5552941..4a6a2a9 100644
--- a/drivers/md/persistent-data/dm-space-map-common.c
+++ b/drivers/md/persistent-data/dm-space-map-common.c
@@ -7,6 +7,7 @@
#include "dm-space-map-common.h"
#include "dm-transaction-manager.h"
#include "dm-btree-internal.h"
+#include "dm-persistent-data-internal.h"
#include <linux/bitops.h>
#include <linux/device-mapper.h>
@@ -1083,28 +1084,92 @@ int sm_ll_open_metadata(struct ll_disk *ll, struct dm_transaction_manager *tm,
/*----------------------------------------------------------------*/
+static inline int ie_cache_writeback(struct ll_disk *ll, struct ie_cache *iec)
+{
+ iec->dirty = false;
+ __dm_bless_for_disk(iec->ie);
+ return dm_btree_insert(&ll->bitmap_info, ll->bitmap_root,
+ &iec->index, &iec->ie, &ll->bitmap_root);
+}
+
+static inline unsigned hash_index(dm_block_t index)
+{
+ return dm_hash_block(index, IE_CACHE_MASK);
+}
+
static int disk_ll_load_ie(struct ll_disk *ll, dm_block_t index,
struct disk_index_entry *ie)
{
- return dm_btree_lookup(&ll->bitmap_info, ll->bitmap_root, &index, ie);
+ int r;
+ unsigned h = hash_index(index);
+ struct ie_cache *iec = ll->ie_cache + h;
+
+ if (iec->valid) {
+ if (iec->index == index) {
+ memcpy(ie, &iec->ie, sizeof(*ie));
+ return 0;
+ }
+
+ if (iec->dirty) {
+ r = ie_cache_writeback(ll, iec);
+ if (r)
+ return r;
+ }
+ }
+
+ r = dm_btree_lookup(&ll->bitmap_info, ll->bitmap_root, &index, ie);
+ if (!r) {
+ iec->valid = true;
+ iec->dirty = false;
+ iec->index = index;
+ memcpy(&iec->ie, ie, sizeof(*ie));
+ }
+
+ return r;
}
static int disk_ll_save_ie(struct ll_disk *ll, dm_block_t index,
struct disk_index_entry *ie)
{
- __dm_bless_for_disk(ie);
- return dm_btree_insert(&ll->bitmap_info, ll->bitmap_root,
- &index, ie, &ll->bitmap_root);
+ int r;
+ unsigned h = hash_index(index);
+ struct ie_cache *iec = ll->ie_cache + h;
+
+ ll->bitmap_index_changed = true;
+ if (iec->valid) {
+ if (iec->index == index) {
+ memcpy(&iec->ie, ie, sizeof(*ie));
+ iec->dirty = true;
+ return 0;
+ }
+
+ if (iec->dirty) {
+ r = ie_cache_writeback(ll, iec);
+ if (r)
+ return r;
+ }
+ }
+
+ iec->valid = true;
+ iec->dirty = true;
+ iec->index = index;
+ memcpy(&iec->ie, ie, sizeof(*ie));
+ return 0;
}
static int disk_ll_init_index(struct ll_disk *ll)
{
+ unsigned i;
+ for (i = 0; i < IE_CACHE_SIZE; i++) {
+ struct ie_cache *iec = ll->ie_cache + i;
+ iec->valid = false;
+ iec->dirty = false;
+ }
return dm_btree_empty(&ll->bitmap_info, &ll->bitmap_root);
}
static int disk_ll_open(struct ll_disk *ll)
{
- /* nothing to do */
return 0;
}
@@ -1115,7 +1180,16 @@ static dm_block_t disk_ll_max_entries(struct ll_disk *ll)
static int disk_ll_commit(struct ll_disk *ll)
{
- return 0;
+ int r = 0;
+ unsigned i;
+
+ for (i = 0; i < IE_CACHE_SIZE; i++) {
+ struct ie_cache *iec = ll->ie_cache + i;
+ if (iec->valid && iec->dirty)
+ r = ie_cache_writeback(ll, iec);
+ }
+
+ return r;
}
int sm_ll_new_disk(struct ll_disk *ll, struct dm_transaction_manager *tm)
diff --git a/drivers/md/persistent-data/dm-space-map-common.h b/drivers/md/persistent-data/dm-space-map-common.h
index 4a22183..706ceb8 100644
--- a/drivers/md/persistent-data/dm-space-map-common.h
+++ b/drivers/md/persistent-data/dm-space-map-common.h
@@ -54,6 +54,20 @@ typedef int (*open_index_fn)(struct ll_disk *ll);
typedef dm_block_t (*max_index_entries_fn)(struct ll_disk *ll);
typedef int (*commit_fn)(struct ll_disk *ll);
+/*
+ * A lot of time can be wasted reading and writing the same
+ * index entry. So we cache a few entries.
+ */
+#define IE_CACHE_SIZE 64
+#define IE_CACHE_MASK (IE_CACHE_SIZE - 1)
+
+struct ie_cache {
+ bool valid;
+ bool dirty;
+ dm_block_t index;
+ struct disk_index_entry ie;
+};
+
struct ll_disk {
struct dm_transaction_manager *tm;
struct dm_btree_info bitmap_info;
@@ -79,6 +93,8 @@ struct ll_disk {
max_index_entries_fn max_entries;
commit_fn commit;
bool bitmap_index_changed:1;
+
+ struct ie_cache ie_cache[IE_CACHE_SIZE];
};
struct disk_sm_root {