diff options
| author | Anton Nefedov <anton.nefedov@virtuozzo.com> | 2019-05-16 17:27:49 +0300 |
|---|---|---|
| committer | Max Reitz <mreitz@redhat.com> | 2019-05-28 20:30:55 +0200 |
| commit | c8bb23cbdbe32f5c326365e0a82e1b0e68cdcd8a (patch) | |
| tree | 7169d73a97be9364e328610798c54f8af16b6fa4 /block/trace-events | |
| parent | 330c72957196e0ae382abcaa97ebf4eb9bc8574f (diff) | |
qcow2: skip writing zero buffers to empty COW areas
If COW areas of the newly allocated clusters are zeroes on the backing
image, efficient bdrv_write_zeroes(flags=BDRV_REQ_NO_FALLBACK) can be
used on the whole cluster instead of writing explicit zero buffers later
in perform_cow().
iotest 060:
write to the discarded cluster does not trigger COW anymore.
Use a backing image instead.
Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com>
Message-id: 20190516142749.81019-2-anton.nefedov@virtuozzo.com
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Diffstat (limited to 'block/trace-events')
| -rw-r--r-- | block/trace-events | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/block/trace-events b/block/trace-events index 79ccd8d824..1e0653ce6d 100644 --- a/block/trace-events +++ b/block/trace-events @@ -68,6 +68,7 @@ qcow2_writev_done_part(void *co, int cur_bytes) "co %p cur_bytes %d" qcow2_writev_data(void *co, uint64_t offset) "co %p offset 0x%" PRIx64 qcow2_pwrite_zeroes_start_req(void *co, int64_t offset, int count) "co %p offset 0x%" PRIx64 " count %d" qcow2_pwrite_zeroes(void *co, int64_t offset, int count) "co %p offset 0x%" PRIx64 " count %d" +qcow2_skip_cow(void *co, uint64_t offset, int nb_clusters) "co %p offset 0x%" PRIx64 " nb_clusters %d" # qcow2-cluster.c qcow2_alloc_clusters_offset(void *co, uint64_t offset, int bytes) "co %p offset 0x%" PRIx64 " bytes %d" |