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authorMikulas Patocka <mpatocka@redhat.com>2014-01-14 04:13:05 +0400
committerMike Snitzer <snitzer@redhat.com>2014-01-15 08:23:03 +0400
commit55b082e614e219fb5199a6f93e648ed35d3c96d5 (patch)
treea2707e62bdd914e9651e78cde6cb55a5f0b88d7f /drivers/md/dm-bufio.c
parent55494bf2947dccdf2d98b62374fea7365dfead84 (diff)
downloadlinux-55b082e614e219fb5199a6f93e648ed35d3c96d5.tar.xz
dm snapshot: use dm-bufio prefetch
This patch modifies dm-snapshot so that it prefetches the buffers when loading the exceptions. The number of buffers read ahead is specified in the DM_PREFETCH_CHUNKS macro. The current value for DM_PREFETCH_CHUNKS (12) was found to provide the best performance on a single 15k SCSI spindle. In the future we may modify this default or make it configurable. Also, introduce the function dm_bufio_set_minimum_buffers to setup bufio's number of internal buffers before freeing happens. dm-bufio may hold more buffers if enough memory is available. There is no guarantee that the specified number of buffers will be available - if you need a guarantee, use the argument reserved_buffers for dm_bufio_client_create. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md/dm-bufio.c')
-rw-r--r--drivers/md/dm-bufio.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index d86593721915..9ed42125514b 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -104,6 +104,8 @@ struct dm_bufio_client {
struct list_head reserved_buffers;
unsigned need_reserved_buffers;
+ unsigned minimum_buffers;
+
struct hlist_head *cache_hash;
wait_queue_head_t free_buffer_wait;
@@ -861,8 +863,8 @@ static void __get_memory_limit(struct dm_bufio_client *c,
buffers = dm_bufio_cache_size_per_client >>
(c->sectors_per_block_bits + SECTOR_SHIFT);
- if (buffers < DM_BUFIO_MIN_BUFFERS)
- buffers = DM_BUFIO_MIN_BUFFERS;
+ if (buffers < c->minimum_buffers)
+ buffers = c->minimum_buffers;
*limit_buffers = buffers;
*threshold_buffers = buffers * DM_BUFIO_WRITEBACK_PERCENT / 100;
@@ -1372,6 +1374,12 @@ void dm_bufio_forget(struct dm_bufio_client *c, sector_t block)
}
EXPORT_SYMBOL(dm_bufio_forget);
+void dm_bufio_set_minimum_buffers(struct dm_bufio_client *c, unsigned n)
+{
+ c->minimum_buffers = n;
+}
+EXPORT_SYMBOL(dm_bufio_set_minimum_buffers);
+
unsigned dm_bufio_get_block_size(struct dm_bufio_client *c)
{
return c->block_size;
@@ -1568,6 +1576,8 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
INIT_LIST_HEAD(&c->reserved_buffers);
c->need_reserved_buffers = reserved_buffers;
+ c->minimum_buffers = DM_BUFIO_MIN_BUFFERS;
+
init_waitqueue_head(&c->free_buffer_wait);
c->async_write_error = 0;