On Tue, Nov 20, 2012 at 4:45 PM, Paolo Bonzini <pbonz...@redhat.com> wrote:
> buffered_rate_limit is called to prevent the RAM migration callback
> from putting too much data in the buffer. So it has to check against
> the amount of data currently in the buffer, not against the amount
> of data that has been transferred so far.
>
> s->bytes_xfer is used to communicate between successive calls of
> buffered_put_buffer. Buffered_rate_tick resets it every now and
> then to prevent moving too much buffered data to the socket at
> once. However, its value does not matter for the producer of the
> data.
>
> Here is the result for migrating an idle guest with 3GB of memory
> and ~360MB of non-zero memory:
>
> migrate_set_speed Before After
> ------------------------------------------------------------
> default (32MB/sec) ~3 sec ~13 sec
> infinite (10GB/sec) ~3 sec ~3 sec
>
> Note that before this patch, QEMU is transferring of 100 MB/sec
> despite the rate limiting.
>
> Also fix an off-by-one error, where > was used instead of >=. With this
> fix, the condition in buffered_put_buffer is really the opposite of
> "rate limit reached", so write it explicitly like that.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> buffered_file.c | 7 ++-----
> 1 files changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/buffered_file.c b/buffered_file.c
> index edead5c..2dac99a 100644
> --- a/buffered_file.c
> +++ b/buffered_file.c
> @@ -125,7 +125,7 @@ static int buffered_put_buffer(void *opaque, const
> uint8_t *buf, int64_t pos, in
>
> if (pos == 0 && size == 0) {
> DPRINTF("file is ready\n");
> - if (!s->freeze_output && s->bytes_xfer < s->xfer_limit) {
> + if (!qemu_file_rate_limit(s->file)) {
> DPRINTF("notifying client\n");
> migrate_fd_put_ready(s->migration_state);
> }
> @@ -190,10 +190,7 @@ static int buffered_rate_limit(void *opaque)
> if (ret) {
> return ret;
> }
> - if (s->freeze_output)
> - return 1;
> -
> - if (s->bytes_xfer > s->xfer_limit)
> + if (s->buffer_size >= s->xfer_limit)
Please add braces.
> return 1;
>
> return 0;
> --
> 1.7.1
>
>
>
