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qapi: backup: disable copy_range by default

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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>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2021-01-17 00:47:00 +03:00 committed by Max Reitz
parent 71eed4cebe
commit 6a30f663d4
2 changed files with 2 additions and 2 deletions
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2
blockdev.c
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@ -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) {

2
qapi/block-core.json
View File

@ -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.