Commit 6b06dd5a authored by Joe Thornber's avatar Joe Thornber Committed by Mike Snitzer
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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: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent be500ed7

drivers/md/persistent-data/dm-space-map-common.c

+80 −6
Original line number Diff line number Diff line
@@ -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)

drivers/md/persistent-data/dm-space-map-common.h

+16 −0
Original line number Diff line number Diff line
@@ -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 {