[Qemu-devel] [PATCH v3 9/9] coalesce adjacent iovecs

[Orit Wasserman]

This way we send one big buffer instead of many small ones

Signed-off-by: Orit Wasserman <owass...@redhat.com>
---
 savevm.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/savevm.c b/savevm.c
index 50e8fb2..13a533b 100644
--- a/savevm.c
+++ b/savevm.c
@@ -634,8 +634,14 @@ void qemu_put_buffer_no_copy(QEMUFile *f, const uint8_t 
*buf, int size)
         abort();
     }
 
-    f->iov[f->iovcnt].iov_base = (uint8_t *)buf;
-    f->iov[f->iovcnt++].iov_len = size;
+    /* check for adjoint buffer and colace them */
+    if (f->iovcnt > 0 && buf == f->iov[f->iovcnt - 1].iov_base +
+        f->iov[f->iovcnt - 1].iov_len) {
+        f->iov[f->iovcnt - 1].iov_len += size;
+    } else {
+        f->iov[f->iovcnt].iov_base = (uint8_t *)buf;
+        f->iov[f->iovcnt++].iov_len = size;
+    }
 
     f->is_write = 1;
     f->bytes_xfer += size;
@@ -690,8 +696,15 @@ void qemu_put_byte(QEMUFile *f, int v)
     f->buf[f->buf_index++] = v;
     f->is_write = 1;
     f->bytes_xfer += 1;
-    f->iov[f->iovcnt].iov_base = f->buf + (f->buf_index - 1);
-    f->iov[f->iovcnt++].iov_len = 1;
+
+    /* check for adjoint buffer and colace them */
+    if (f->iovcnt > 0 && f->buf + (f->buf_index - 1)  ==
+        f->iov[f->iovcnt - 1].iov_base + f->iov[f->iovcnt - 1].iov_len) {
+        f->iov[f->iovcnt - 1].iov_len += 1;
+    } else {
+        f->iov[f->iovcnt].iov_base = f->buf + (f->buf_index - 1);
+        f->iov[f->iovcnt++].iov_len = 1;
+    }
 
     if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
         qemu_fflush(f);
-- 
1.7.11.7