From: Peter Xu <[email protected]>

Put buffer can be async as long as the flush happens before the buffer will
be recycled / reused.  Do it for postcopy package data.  Quick measurement
shows a small VM the time to push / flush the package shrinks from 91us to
38us.

Signed-off-by: Peter Xu <[email protected]>
Reviewed-by: Fabiano Rosas <[email protected]>
Tested-by: Lukas Straub <[email protected]>
Link: 
https://lore.kernel.org/qemu-devel/[email protected]
Signed-off-by: Fabiano Rosas <[email protected]>
---
 migration/savevm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 9d2109718a..d41e89228d 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1136,7 +1136,8 @@ int qemu_savevm_send_packaged(QEMUFile *f, const uint8_t 
*buf, size_t len)
     trace_qemu_savevm_send_packaged();
     qemu_savevm_command_send(f, MIG_CMD_PACKAGED, 4, (uint8_t *)&tmp);
 
-    qemu_put_buffer(f, buf, len);
+    /* We can use async put because the qemufile will be flushed right away */
+    qemu_put_buffer_async(f, buf, len, false);
     qemu_fflush(f);
 
     return 0;
-- 
2.51.0


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