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 v4, 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 v4: - Patch 6: Initialize the QEMUIOVector with only 1 iovecs [Kevin] - Patch 7: Initialize the QEMUIOVector with 2 + m->data_qiov->niov [Kevin] - Patch 7: Rename can_merge_cow() to merge_cow() [Kevin] v3: https://lists.gnu.org/archive/html/qemu-block/2017-06/msg00472.html - Patch 4: Over-allocate the read buffer in perform_cow() so both COW sectors are optimally aligned [Eric] v2: https://lists.gnu.org/archive/html/qemu-block/2017-06/msg00227.html - 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 v3: 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:[----] [--] 'qcow2: Split do_perform_cow() into _read(), _encrypt() and _write()' 005/7:[----] [--] 'qcow2: Allow reading both COW regions with only one request' 006/7:[0002] [FC] 'qcow2: Pass a QEMUIOVector to do_perform_cow_{read,write}()' 007/7:[0008] [FC] '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
