On 09/17/2013 07:48 AM, Peter Lieven wrote: > Signed-off-by: Peter Lieven <p...@kamp.de> > --- > block.c | 57 +++++++++++++++++++++++++++++++++++++++++---------------- > 1 file changed, 41 insertions(+), 16 deletions(-) > > diff --git a/block.c b/block.c > index 177720e..74ec342 100644 > --- a/block.c > +++ b/block.c > @@ -2660,28 +2660,53 @@ static int coroutine_fn > bdrv_co_do_write_zeroes(BlockDriverState *bs, > BlockDriver *drv = bs->drv; > QEMUIOVector qiov; > struct iovec iov; > - int ret; > + int ret = 0; > > - /* TODO Emulate only part of misaligned requests instead of letting block > - * drivers return -ENOTSUP and emulate everything */ > + /* if no limit is specified in the BlockDriverState use a default > + * of 32768 512-byte sectors (16 MiB) per request. > + */ > + int max_write_zeroes = bs->max_write_zeroes ? bs->max_write_zeroes : > 32768;
Worth having a named constant instead of a magic number? > + while (nb_sectors > 0 && !ret) { > + > + if (ret == -ENOTSUP) { > + /* Fall back to bounce buffer if write zeroes is unsupported */ > + iov.iov_len = nb_sectors * BDRV_SECTOR_SIZE; > + iov.iov_base = qemu_blockalign(bs, iov.iov_len); > + memset(iov.iov_base, 0, iov.iov_len); This allocates, clears, and frees iov.iov_len bytes of 0 every iteration through the loop. Can you hoist that so you only allocate the bounce buffer once, and then clean it up after the loop completes? -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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