d61790112f
This is preparational commit for tweaks in Parallels image expansion. The idea is that enlarge via truncate by one data block is slow. It would be much better to use fallocate via bdrv_write_zeroes and expand by some significant amount at once. Original idea with sequential file writing to the end of the file without fallocate/truncate would be slower than this approach if the image is expanded with several operations: - each image expanding means file metadata update, i.e. filesystem journal write. Truncate/write to newly truncated space update file metadata twice thus truncate removal helps. With fallocate call inside bdrv_write_zeroes file metadata is updated only once and this should happen infrequently thus this approach is the best one for the image expansion - tail writes are ordered, i.e. the guest IO queue could not be sent immediately to the host introducing additional IO delays This patch just adds proper parameters into BDRVParallelsState and performs options parsing in parallels_open. Signed-off-by: Denis V. Lunev <den@openvz.org> Reviewed-by: Roman Kagan <rkagan@parallels.com> Signed-off-by: Roman Kagan <rkagan@parallels.com> Message-id: 1430207220-24458-26-git-send-email-den@openvz.org CC: Roman Kagan <rkagan@parallels.com> CC: Kevin Wolf <kwolf@redhat.com> CC: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Read the documentation in qemu-doc.html or on http://wiki.qemu-project.org - QEMU team