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authorMike Snitzer <snitzer@redhat.com>2009-12-10 23:52:34 +0000
committerAlasdair G Kergon <agk@redhat.com>2009-12-10 23:52:34 +0000
commit8a2d528620e228ddfd0df9cec0a16e034ff8db1d (patch)
treeff93eac3e996df7bf046d08c7386d690c3fd5ee0 /drivers/md
parent73dfd078cf8bfee4018fb22f1e2a24f2e05b69dc (diff)
downloadop-kernel-dev-8a2d528620e228ddfd0df9cec0a16e034ff8db1d.zip
op-kernel-dev-8a2d528620e228ddfd0df9cec0a16e034ff8db1d.tar.gz
dm snapshot: merge consecutive chunks together
s->store->type->prepare_merge returns the number of chunks that can be copied linearly working backwards from the returned chunk number. For example, if it returns 3 chunks with old_chunk == 10 and new_chunk == 20, then chunk 20 can be copied to 10, chunk 19 to 9 and 18 to 8. Until now kcopyd only copied one chunk at a time. This patch now copies the full set at once. Consequently, snapshot_merge_process() needs to delay the merging of all chunks if any have writes in progress, not just the first chunk in the region that is to be merged. snapshot-merge's performance is now comparable to the original snapshot-origin target. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-snap.c31
1 files changed, 21 insertions, 10 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 1498704..bb4b733 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -879,9 +879,10 @@ static void increment_pending_exceptions_done_count(void)
static void snapshot_merge_next_chunks(struct dm_snapshot *s)
{
- int r;
+ int i, linear_chunks;
chunk_t old_chunk, new_chunk;
struct dm_io_region src, dest;
+ sector_t io_size;
uint64_t previous_count;
BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits));
@@ -896,20 +897,28 @@ static void snapshot_merge_next_chunks(struct dm_snapshot *s)
goto shut;
}
- r = s->store->type->prepare_merge(s->store, &old_chunk, &new_chunk);
- if (r <= 0) {
- if (r < 0)
+ linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
+ &new_chunk);
+ if (linear_chunks <= 0) {
+ if (linear_chunks < 0)
DMERR("Read error in exception store: "
"shutting down merge");
goto shut;
}
- /* TODO: use larger I/O size once we verify that kcopyd handles it */
+ /* Adjust old_chunk and new_chunk to reflect start of linear region */
+ old_chunk = old_chunk + 1 - linear_chunks;
+ new_chunk = new_chunk + 1 - linear_chunks;
+
+ /*
+ * Use one (potentially large) I/O to copy all 'linear_chunks'
+ * from the exception store to the origin
+ */
+ io_size = linear_chunks * s->store->chunk_size;
dest.bdev = s->origin->bdev;
dest.sector = chunk_to_sector(s->store, old_chunk);
- dest.count = min((sector_t)s->store->chunk_size,
- get_dev_size(dest.bdev) - dest.sector);
+ dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector);
src.bdev = s->cow->bdev;
src.sector = chunk_to_sector(s->store, new_chunk);
@@ -925,7 +934,7 @@ static void snapshot_merge_next_chunks(struct dm_snapshot *s)
* significant impact on performance.
*/
previous_count = read_pending_exceptions_done_count();
- while (origin_write_extent(s, dest.sector, s->store->chunk_size)) {
+ while (origin_write_extent(s, dest.sector, io_size)) {
wait_event(_pending_exceptions_done,
(read_pending_exceptions_done_count() !=
previous_count));
@@ -935,10 +944,12 @@ static void snapshot_merge_next_chunks(struct dm_snapshot *s)
down_write(&s->lock);
s->first_merging_chunk = old_chunk;
- s->num_merging_chunks = 1;
+ s->num_merging_chunks = linear_chunks;
up_write(&s->lock);
- __check_for_conflicting_io(s, old_chunk);
+ /* Wait until writes to all 'linear_chunks' drain */
+ for (i = 0; i < linear_chunks; i++)
+ __check_for_conflicting_io(s, old_chunk + i);
dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s);
return;
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