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.
Reviewed-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Peter Lieven <p...@kamp.de>
---
qemu-img.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/qemu-img.c b/qemu-img.c
index 0c2e557..15f423b 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;
@@ -1531,7 +1541,7 @@ static int img_convert(int argc, char **argv)
sector_num_next_status = sector_num + n1;
}
- n = MIN(nb_sectors, IO_BUF_SIZE / 512);
+ n = MIN(nb_sectors, bufsectors);
n = MIN(n, bs_sectors - (sector_num - bs_offset));
n1 = n;
--
1.7.9.5
