Il 26/11/2013 09:56, Peter Lieven ha scritto:
> since the convert process is basically a sync operation it might
> be benificial in some case to change the hardcoded I/O buffer
> size to a greater value.
>
> This patch increases the I/O buffer size if the output
> driver advertises an optimal transfer length or discard alignment
> that is greater than the default buffer size of 2M.
>
> Signed-off-by: Peter Lieven <p...@kamp.de>
> ---
> qemu-img.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/qemu-img.c b/qemu-img.c
> index e2d1a0a..b076d44 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -1135,6 +1135,7 @@ static int img_convert(int argc, char **argv)
> sector_num_next_status = 0;
> uint64_t bs_sectors;
> uint8_t * buf = NULL;
> + size_t bufsectors = IO_BUF_SIZE / BDRV_SECTOR_SIZE;
> const uint8_t *buf1;
> BlockDriverInfo bdi;
> QEMUOptionParameter *param = NULL, *create_options = NULL;
> @@ -1371,7 +1372,16 @@ static int img_convert(int argc, char **argv)
> bs_i = 0;
> bs_offset = 0;
> bdrv_get_geometry(bs[0], &bs_sectors);
> - buf = qemu_blockalign(out_bs, IO_BUF_SIZE);
> +
> + /* increase bufsectors from the default 4096 (2M) if opt_transfer_length
> + * or discard_alignment of the out_bs is greater. Limit to 32768 (16MB)
> + * as maximum. */
> + bufsectors = MIN(32768,
> + MAX(bufsectors, MAX(out_bs->bl.opt_transfer_length,
> + out_bs->bl.discard_alignment))
> + );
> +
> + buf = qemu_blockalign(out_bs, bufsectors * BDRV_SECTOR_SIZE);
>
> if (skip_create) {
> int64_t output_length = bdrv_getlength(out_bs);
> @@ -1394,7 +1404,7 @@ static int img_convert(int argc, char **argv)
> goto out;
> }
> cluster_size = bdi.cluster_size;
> - if (cluster_size <= 0 || cluster_size > IO_BUF_SIZE) {
> + if (cluster_size <= 0 || cluster_size > bufsectors *
> BDRV_SECTOR_SIZE) {
> error_report("invalid cluster size");
> ret = -1;
> goto out;
> @@ -1531,8 +1541,8 @@ static int img_convert(int argc, char **argv)
> sector_num_next_status = sector_num + n1;
> }
>
> - if (nb_sectors >= (IO_BUF_SIZE / 512)) {
> - n = (IO_BUF_SIZE / 512);
> + if (nb_sectors >= bufsectors) {
> + n = bufsectors;
> } else {
> n = nb_sectors;
> }
>
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
