Well, I think this is the first real improve patch.
Is more a RFC than a patch. Yes, some lines are terrible!
It collapses refcount decrement during cow.
>From a first check time executing 015 test passed from about 600 seconds
to 70.
This at least prove that refcount updates counts!
Some doubt:
1- place the code in qcow2-refcount.c as it update only refcount and not
cluster?
2- allow some sort of "begin transaction" / "commit" / "rollback" like
databases instead?
3- allow changing tables from different coroutines?
1) If you have a sequence like (1, 2, 4) probably these clusters are all in
the same l2 table but with this code you get two write instead of one.
I'm thinking about a function in qcow2-refcount.c that accept an array of
cluster
instead of a start + len.
Signed-off-by: Frediano Ziglio <fredd...@gmail.com>
---
block/qcow2-cluster.c | 36 ++++++++++++++++++++++++++++++++++--
1 files changed, 34 insertions(+), 2 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 81cf77d..da17365 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -675,10 +675,42 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs,
QCowL2Meta *m)
* Also flush bs->file to get the right order for L2 and refcount update.
*/
if (j != 0) {
+ int64_t old_start = 0, old_end = -2;
+ int count = 0;
for (i = 0; i < j; i++) {
- qcow2_free_any_clusters(bs,
- be64_to_cpu(old_cluster[i]) & ~QCOW_OFLAG_COPIED, 1);
+ old_cluster[i] = be64_to_cpu(old_cluster[i]) & ~QCOW_OFLAG_COPIED;
}
+ // XXX sort old_cluster
+ for (i = 0; i < j; i++) {
+ int64_t cluster = old_cluster[i];
+
+ /* group if contiguos */
+ if (old_end + 1 == (cluster >> s->cluster_bits)) {
+ ++old_end;
+ continue;
+ }
+
+ /* handle */
+ if (old_end > 0) {
+ qcow2_free_any_clusters(bs, old_start << s->cluster_bits,
old_end - old_start + 1);
+ count += old_end - old_start + 1;
+ }
+ old_end = -2;
+
+ /* handle compressed separately */
+ if ((cluster & QCOW_OFLAG_COMPRESSED)) {
+ qcow2_free_any_clusters(bs, cluster, 1);
+ continue;
+ }
+
+ /* start a new group */
+ old_start = old_end = cluster >> s->cluster_bits;
+ }
+ if (old_end > 0) {
+ qcow2_free_any_clusters(bs, old_start << s->cluster_bits, old_end
- old_start + 1);
+ count += old_end - old_start + 1;
+ }
+ assert(count == j);
}
ret = 0;
--
1.7.1
