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authorJoe Thornber <ejt@redhat.com>2014-10-06 15:27:26 +0100
committerMike Snitzer <snitzer@redhat.com>2014-11-10 15:25:26 -0500
commit4646015d7e4ca5a4dc19427fb0a0aeff15a4fd91 (patch)
tree5afe82e874f9eff6eeb70e77db458b22dcea3307
parente5cfc69a513cdc9d9e753c5ce07f0cc6b496bfd3 (diff)
downloadlinux-4646015d7e4ca5a4dc19427fb0a0aeff15a4fd91.tar.gz
dm transaction manager: add support for prefetching blocks of metadata
Introduce the dm_tm_issue_prefetches interface. If you're using a non-blocking clone the tm will build up a list of requested blocks that weren't in core. dm_tm_issue_prefetches will request those blocks to be prefetched. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
-rw-r--r--drivers/md/persistent-data/dm-transaction-manager.c77
-rw-r--r--drivers/md/persistent-data/dm-transaction-manager.h7
2 files changed, 82 insertions, 2 deletions
diff --git a/drivers/md/persistent-data/dm-transaction-manager.c b/drivers/md/persistent-data/dm-transaction-manager.c
index 3bc30a0ae3d6..9cb797d800cf 100644
--- a/drivers/md/persistent-data/dm-transaction-manager.c
+++ b/drivers/md/persistent-data/dm-transaction-manager.c
@@ -10,6 +10,8 @@
#include "dm-persistent-data-internal.h"
#include <linux/export.h>
+#include <linux/mutex.h>
+#include <linux/hash.h>
#include <linux/slab.h>
#include <linux/device-mapper.h>
@@ -17,6 +19,61 @@
/*----------------------------------------------------------------*/
+#define PREFETCH_SIZE 128
+#define PREFETCH_BITS 7
+#define PREFETCH_SENTINEL ((dm_block_t) -1ULL)
+
+struct prefetch_set {
+ struct mutex lock;
+ dm_block_t blocks[PREFETCH_SIZE];
+};
+
+static unsigned prefetch_hash(dm_block_t b)
+{
+ return hash_64(b, PREFETCH_BITS);
+}
+
+static void prefetch_wipe(struct prefetch_set *p)
+{
+ unsigned i;
+ for (i = 0; i < PREFETCH_SIZE; i++)
+ p->blocks[i] = PREFETCH_SENTINEL;
+}
+
+static void prefetch_init(struct prefetch_set *p)
+{
+ mutex_init(&p->lock);
+ prefetch_wipe(p);
+}
+
+static void prefetch_add(struct prefetch_set *p, dm_block_t b)
+{
+ unsigned h = prefetch_hash(b);
+
+ mutex_lock(&p->lock);
+ if (p->blocks[h] == PREFETCH_SENTINEL)
+ p->blocks[h] = b;
+
+ mutex_unlock(&p->lock);
+}
+
+static void prefetch_issue(struct prefetch_set *p, struct dm_block_manager *bm)
+{
+ unsigned i;
+
+ mutex_lock(&p->lock);
+
+ for (i = 0; i < PREFETCH_SIZE; i++)
+ if (p->blocks[i] != PREFETCH_SENTINEL) {
+ dm_bm_prefetch(bm, p->blocks[i]);
+ p->blocks[i] = PREFETCH_SENTINEL;
+ }
+
+ mutex_unlock(&p->lock);
+}
+
+/*----------------------------------------------------------------*/
+
struct shadow_info {
struct hlist_node hlist;
dm_block_t where;
@@ -37,6 +94,8 @@ struct dm_transaction_manager {
spinlock_t lock;
struct hlist_head buckets[DM_HASH_SIZE];
+
+ struct prefetch_set prefetches;
};
/*----------------------------------------------------------------*/
@@ -117,6 +176,8 @@ static struct dm_transaction_manager *dm_tm_create(struct dm_block_manager *bm,
for (i = 0; i < DM_HASH_SIZE; i++)
INIT_HLIST_HEAD(tm->buckets + i);
+ prefetch_init(&tm->prefetches);
+
return tm;
}
@@ -268,8 +329,14 @@ int dm_tm_read_lock(struct dm_transaction_manager *tm, dm_block_t b,
struct dm_block_validator *v,
struct dm_block **blk)
{
- if (tm->is_clone)
- return dm_bm_read_try_lock(tm->real->bm, b, v, blk);
+ if (tm->is_clone) {
+ int r = dm_bm_read_try_lock(tm->real->bm, b, v, blk);
+
+ if (r == -EWOULDBLOCK)
+ prefetch_add(&tm->real->prefetches, b);
+
+ return r;
+ }
return dm_bm_read_lock(tm->bm, b, v, blk);
}
@@ -317,6 +384,12 @@ struct dm_block_manager *dm_tm_get_bm(struct dm_transaction_manager *tm)
return tm->bm;
}
+void dm_tm_issue_prefetches(struct dm_transaction_manager *tm)
+{
+ prefetch_issue(&tm->prefetches, tm->bm);
+}
+EXPORT_SYMBOL_GPL(dm_tm_issue_prefetches);
+
/*----------------------------------------------------------------*/
static int dm_tm_create_internal(struct dm_block_manager *bm,
diff --git a/drivers/md/persistent-data/dm-transaction-manager.h b/drivers/md/persistent-data/dm-transaction-manager.h
index 2772ed2a781a..2e0d4d66fb1b 100644
--- a/drivers/md/persistent-data/dm-transaction-manager.h
+++ b/drivers/md/persistent-data/dm-transaction-manager.h
@@ -109,6 +109,13 @@ int dm_tm_ref(struct dm_transaction_manager *tm, dm_block_t b,
struct dm_block_manager *dm_tm_get_bm(struct dm_transaction_manager *tm);
/*
+ * If you're using a non-blocking clone the tm will build up a list of
+ * requested blocks that weren't in core. This call will request those
+ * blocks to be prefetched.
+ */
+void dm_tm_issue_prefetches(struct dm_transaction_manager *tm);
+
+/*
* A little utility that ties the knot by producing a transaction manager
* that has a space map managed by the transaction manager...
*