Am 07.06.2017 um 16:08 hat Alberto Garcia geschrieben: > Instead of passing a single buffer pointer to do_perform_cow_write(), > pass a QEMUIOVector. This will allow us to merge the write requests > for the COW regions and the actual data into a single one. > > Although do_perform_cow_read() does not strictly need to change its > API, we're doing it here as well for consistency. > > Signed-off-by: Alberto Garcia <be...@igalia.com> > --- > block/qcow2-cluster.c | 51 > ++++++++++++++++++++++++--------------------------- > 1 file changed, 24 insertions(+), 27 deletions(-)
> @@ -807,22 +798,25 @@ static int perform_cow(BlockDriverState *bs, QCowL2Meta > *m) > /* The part of the buffer where the end region is located */ > end_buffer = start_buffer + buffer_size - end->nb_bytes; > > + qemu_iovec_init(&qiov, 3); > + You don't actually make use of more than one iovec in this patch. And after the last patch, the value is potentially too low - which isn't fatal because this is not a fixed maximum, but just a hint, but it can cause unnecessary memory allocations. It would probably be better to use 1 here and change it into 2 + m->data_qiov->niov when you add write merging. Kevin
