Am 12.07.2018 um 15:00 hat Peter Lieven geschrieben: > We currently don't enforce that the sparse segments we detect during convert > are > aligned. This leads to unnecessary and costly read-modify-write cycles either > internally in Qemu or in the background on the storage device as nearly all > modern filesystems or hardware have a 4k alignment internally. > > This patch modifies is_allocated_sectors so that its *pnum result will always > end at an alignment boundary. This way all requests will end at an alignment > boundary. The start of all requests will also be aligned as long as the > results > of get_block_status do not lead to an unaligned offset. > > The number of RMW cycles when converting an example image [1] to a raw device > that > has 4k sector size is about 4600 4k read requests to perform a total of about > 15000 > write requests. With this path the additional 4600 read requests are > eliminated while > the number of total write requests stays constant. > > [1] > https://cloud-images.ubuntu.com/releases/16.04/release/ubuntu-16.04-server-cloudimg-amd64-disk1.vmdk > > Signed-off-by: Peter Lieven <p...@kamp.de>
Thanks, applied to the block branch. Kevin
