Hi all,
here's a patch series that rewrites the copy-on-write code in the
qcow2 driver to reduce the number of I/O operations.
This is version v3, please refer to the original e-mail for a complete
description:
https://lists.gnu.org/archive/html/qemu-block/2017-05/msg00882.html
Regards,
Berto
v3:
- Patch 4: Over-allocate the read buffer in perform_cow() so both COW
sectors are optimally aligned [Eric]
v2:
- Patch 1: Update commit message [Eric]
- Patch 7: Make sure that the number of iovs does not exceed IOV_MAX [Anton]
- Patch 7: Don't add zero-length buffers to the qiov in perform_cow()
v1: https://lists.gnu.org/archive/html/qemu-block/2017-05/msg00882.html
- Initial version
Output of git-backport-diff against v2:
Key:
[----] : patches are identical
[####] : number of functional differences between upstream/downstream patch
[down] : patch is downstream-only
The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively
001/7:[----] [--] 'qcow2: Remove unused Error variable in do_perform_cow()'
002/7:[----] [--] 'qcow2: Use unsigned int for both members of Qcow2COWRegion'
003/7:[----] [--] 'qcow2: Make perform_cow() call do_perform_cow() twice'
004/7:[0009] [FC] 'qcow2: Split do_perform_cow() into _read(), _encrypt() and _write()'
005/7:[0026] [FC] 'qcow2: Allow reading both COW regions with only one request'
006/7:[----] [-C] 'qcow2: Pass a QEMUIOVector to do_perform_cow_{read,write}()'
007/7:[----] [-C] 'qcow2: Merge the writing of the COW regions with the guest data'
Alberto Garcia (7):
qcow2: Remove unused Error variable in do_perform_cow()
qcow2: Use unsigned int for both members of Qcow2COWRegion
qcow2: Make perform_cow() call do_perform_cow() twice
qcow2: Split do_perform_cow() into _read(), _encrypt() and _write()
qcow2: Allow reading both COW regions with only one request
qcow2: Pass a QEMUIOVector to do_perform_cow_{read,write}()
qcow2: Merge the writing of the COW regions with the guest data
block/qcow2-cluster.c | 201 ++++++++++++++++++++++++++++++++++++++------------
block/qcow2.c | 64 +++++++++++++---
block/qcow2.h | 11 ++-
3 files changed, 216 insertions(+), 60 deletions(-)
--
2.11.0