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Re: [Qemu-devel] [PATCH] QEMUFileBuffered: indicate that we're ready whe


From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH] QEMUFileBuffered: indicate that we're ready when the underlying file is ready
Date: Thu, 19 Aug 2010 10:19:43 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.11) Gecko/20100713 Lightning/1.0b1 Thunderbird/3.0.6

On 07/07/2010 11:44 AM, Avi Kivity wrote:
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<address@hidden>\

Applied.  Thanks.

Regards,

Anthony Liguori
---
  buffered_file.c |    8 ++++++++
  1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/buffered_file.c b/buffered_file.c
index 54dc6c2..a79264f 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;
  }





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