Re: [Qemu-devel] [PATCH] QEMUFileBuffered: indicate that we're ready when the underlying file is ready

[Anthony Liguori <anthony@codemonkey.ws>]

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<avi@redhat.com>\
>    

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;
>   }
>
>