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[Qemu-devel] [PATCH v3 00/13] qcow2: space preallocation and COW improve
From: |
Anton Nefedov |
Subject: |
[Qemu-devel] [PATCH v3 00/13] qcow2: space preallocation and COW improvements |
Date: |
Mon, 31 Jul 2017 19:21:52 +0300 |
Here goes a revisited series on qcow2 preallocation. It's probably a bit better
integrated this time and the amount of code is reduced significantly.
Changes in v3:
- requests intersection detection from the previous versions is removed
from qcow2 driver. Instead, tracked request infrastructure from the common
block layer is used.
- that made possible to omit preallocation for metadata writes.
Those are rare and won't affect performance.
- 'Simultaneous writes' feature (patches v2 12-15) dropped by now;
Might worth a separate series.
- various remarks to the previous version fixed
- some iotests added
========
Changes in v2:
- introduce new BDRV flag for write_zeroes()
instead of using driver callback directly.
Skipped introducing new functions like bdrv_co_pallocate() for now:
1. it seems ok to keep calling this write_zeroes() as zeroes
are expected;
2. most of the code can be reused now anyway, so changes to
write_zeroes() path are not significant
3. write_zeroes() alignment and max-request limits can also be reused
As a possible alternative we can have bdrv_co_pallocate() which can
switch to pwrite_zeroes(,flags|=BDRV_REQ_ALLOCATE) early.
========
This pull request is to address a few performance problems of qcow2 format:
1. non cluster-aligned write requests (to unallocated clusters) explicitly
pad data with zeroes if there is no backing data. This can be avoided
and the whole clusters are preallocated and zeroed in a single
efficient write_zeroes() operation, also providing better host file
continuity
2. moreover, efficient write_zeroes() operation can be used to preallocate
space megabytes ahead which gives noticeable improvement on some storage
types (e.g. distributed storages where space allocation operation is
expensive)
/* omitted in v3: */
3. preallocating/zeroing the clusters in advance makes possible to enable
simultaneous writes to the same unallocated cluster, which is beneficial
for parallel sequential write operations which are not cluster-aligned
Performance test results are added to commit messages (see patch 3, 12)
Anton Nefedov (10):
block: introduce BDRV_REQ_ALLOCATE flag
block: treat BDRV_REQ_ALLOCATE as serialising
file-posix: support BDRV_REQ_ALLOCATE
block: support BDRV_REQ_ALLOCATE in passthrough drivers
qcow2: set inactive flag
qcow2: move is_zero_sectors() up
qcow2: skip writing zero buffers to empty COW areas
qcow2: allocate image space by-cluster
iotest 190: test BDRV_REQ_ALLOCATE
iotest 134: test cluster-misaligned encrypted write
Denis V. Lunev (2):
qcow2: preallocation at image expand
qcow2: truncate preallocated space
Pavel Butsykin (1):
qcow2: check space leak at the end of the image
include/block/block.h | 6 +-
include/block/block_int.h | 2 +-
block/qcow2.h | 18 ++++
block/blkdebug.c | 3 +-
block/file-posix.c | 9 +-
block/io.c | 47 +++++++--
block/qcow2-cluster.c | 14 ++-
block/qcow2-refcount.c | 7 ++
block/qcow2.c | 201 +++++++++++++++++++++++++++++++++----
block/raw-format.c | 3 +-
block/trace-events | 2 +
qemu-options.hx | 4 +
tests/qemu-iotests/026.out | 104 ++++++++++++++-----
tests/qemu-iotests/026.out.nocache | 104 ++++++++++++++-----
tests/qemu-iotests/029.out | 5 +-
tests/qemu-iotests/060 | 2 +-
tests/qemu-iotests/060.out | 13 ++-
tests/qemu-iotests/061.out | 5 +-
tests/qemu-iotests/066 | 2 +-
tests/qemu-iotests/066.out | 9 +-
tests/qemu-iotests/098.out | 7 +-
tests/qemu-iotests/108.out | 5 +-
tests/qemu-iotests/112.out | 5 +-
tests/qemu-iotests/134 | 9 ++
tests/qemu-iotests/134.out | 10 ++
tests/qemu-iotests/190 | 146 +++++++++++++++++++++++++++
tests/qemu-iotests/190.out | 50 +++++++++
tests/qemu-iotests/group | 1 +
28 files changed, 693 insertions(+), 100 deletions(-)
create mode 100755 tests/qemu-iotests/190
create mode 100644 tests/qemu-iotests/190.out
--
2.7.4
- [Qemu-devel] [PATCH v3 00/13] qcow2: space preallocation and COW improvements,
Anton Nefedov <=
- [Qemu-devel] [PATCH v3 02/13] block: treat BDRV_REQ_ALLOCATE as serialising, Anton Nefedov, 2017/07/31
- [Qemu-devel] [PATCH v3 07/13] qcow2: truncate preallocated space, Anton Nefedov, 2017/07/31
- [Qemu-devel] [PATCH v3 03/13] file-posix: support BDRV_REQ_ALLOCATE, Anton Nefedov, 2017/07/31
- [Qemu-devel] [PATCH v3 04/13] block: support BDRV_REQ_ALLOCATE in passthrough drivers, Anton Nefedov, 2017/07/31
- [Qemu-devel] [PATCH v3 06/13] qcow2: set inactive flag, Anton Nefedov, 2017/07/31
- [Qemu-devel] [PATCH v3 01/13] block: introduce BDRV_REQ_ALLOCATE flag, Anton Nefedov, 2017/07/31
- [Qemu-devel] [PATCH v3 05/13] qcow2: preallocation at image expand, Anton Nefedov, 2017/07/31
- [Qemu-devel] [PATCH v3 09/13] qcow2: move is_zero_sectors() up, Anton Nefedov, 2017/07/31