qapi: backup: disable copy_range by default

Further commit will add a benchmark
(scripts/simplebench/bench-backup.py), which will show that backup
works better with async parallel requests (previous commit) and
disabled copy_range. So, let's disable copy_range by default.

Note: the option was added several commits ago with default to true,
to follow old behavior (the feature was enabled unconditionally), and
only now we are going to change the default behavior.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-Id: <20210116214705.822267-19-vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

diff --git a/blockdev.c b/blockdev.c
index 25aaacf2535f2e08291fbb04d88ce486f593ecfc..93417f630218ced6265c9eb6b5e76d36f8b693e6 100644 (file)
--- a/blockdev.c
+++ b/blockdev.c
@@ -2829,7 +2829,7 @@ static BlockJob *do_backup_common(BackupCommon *backup,
 {
     BlockJob *job = NULL;
     BdrvDirtyBitmap *bmap = NULL;
-    BackupPerf perf = { .use_copy_range = true, .max_workers = 64 };
+    BackupPerf perf = { .max_workers = 64 };
     int job_flags = JOB_DEFAULT;
 
     if (!backup->has_speed) {

diff --git a/qapi/block-core.json b/qapi/block-core.json
index abcd41ed63062dfa5bcb7e0150d6733787fa2c91..9f555d5c1d83c061d7d8accfcd9287c69e036dec 100644 (file)
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1377,7 +1377,7 @@
 # Optional parameters for backup. These parameters don't affect
 # functionality, but may significantly affect performance.
 #
-# @use-copy-range: Use copy offloading. Default true.
+# @use-copy-range: Use copy offloading. Default false.
 #
 # @max-workers: Maximum number of parallel requests for the sustained background
 #               copying process. Doesn't influence copy-before-write operations.