When doing convert, we check that the sectors that are written
are not empty. When holes are small, and interleaved with data
it can lead to a significant performance issue.
Signed-off-by: Yehuda Sadeh <yehuda@xxxxxxxxxxxxxxx>
---
qemu-img.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/qemu-img.c b/qemu-img.c
index 0552746..757fc3a 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -623,6 +623,7 @@ static int compare_sectors(const uint8_t *buf1, const uint8_t *buf2, int n,
#define IO_BUF_SIZE (2 * 1024 * 1024)
#define IO_WRITE_WINDOW_THRESHOLD (32 * 1024 * 1024)
+#define IO_WRITE_MIN_SIZE (128 * 1024)
static int write_window = 0;
@@ -991,6 +992,7 @@ static int img_convert(int argc, char **argv)
should add a specific call to have the info to go faster */
buf1 = buf;
while (n > 0) {
+ int is_allocated = is_allocated_sectors(buf1, n, &n1);
while (write_window > IO_WRITE_WINDOW_THRESHOLD / 512) {
qemu_aio_wait();
}
@@ -1001,8 +1003,8 @@ static int img_convert(int argc, char **argv)
If the output is to a host device, we also write out
sectors that are entirely 0, since whatever data was
already there is garbage, not 0s. */
- if (!has_zero_init || out_baseimg ||
- is_allocated_sectors(buf1, n, &n1)) {
+ if (is_allocated || n != n1 || !has_zero_init || out_baseimg) {
+ n1 = MAX(n1, MIN(n, IO_WRITE_MIN_SIZE / 512));
QEMUIOVector *qiov = qemu_mallocz(sizeof(QEMUIOVector));
qemu_iovec_init(qiov, 1);
qemu_iovec_add(qiov, (void *)buf1, n1 * 512);
--
1.7.5.1
--
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