Patchwork [2/4] QEMUFileBuffered: indicate that we're ready when the underlying file is ready

login
register
mail settings
Submitter Luiz Capitulino
Date Aug. 19, 2010, 1:18 p.m.
Message ID <1282223922-5971-3-git-send-email-lcapitulino@redhat.com>
Download mbox | patch
Permalink /patch/62155/
State New
Headers show

Comments

Luiz Capitulino - Aug. 19, 2010, 1:18 p.m.
From: Avi Kivity <avi@redhat.com>

QEMUFileBuffered stops writing when the underlying QEMUFile is not ready,
and tells its producer so.  However, when the underlying QEMUFile becomes
ready, it neglects to pass that information along, resulting in stoppage
of all data until the next tick (a tenths of a second).

Usually this doesn't matter, because most QEMUFiles used with QEMUFileBuffered
are almost always ready, but in the case of exec: migration this is not true,
due to the small pipe buffers used to connect to the target process.  The
result is very slow migration.

Fix by detecting the readiness notification and propagating it.  The detection
is a little ugly since QEMUFile overloads put_buffer() to send it, but that's
the suject for a different patch.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
---
 buffered_file.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

Patch

diff --git a/buffered_file.c b/buffered_file.c
index be147d6..1836e7e 100644
--- a/buffered_file.c
+++ b/buffered_file.c
@@ -156,6 +156,14 @@  static int buffered_put_buffer(void *opaque, const uint8_t *buf, int64_t pos, in
         offset = size;
     }
 
+    if (pos == 0 && size == 0) {
+        DPRINTF("file is ready\n");
+        if (s->bytes_xfer <= s->xfer_limit) {
+            DPRINTF("notifying client\n");
+            s->put_ready(s->opaque);
+        }
+    }
+
     return offset;
 }