On Fri, Sep 13, 2019 at 3:36 PM Thomas Higdon <[email protected]> wrote:
>
> Neal Cardwell mentioned that snd_wnd would be useful for diagnosing TCP
> performance problems --
> > (1) Usually when we're diagnosing TCP performance problems, we do so
> > from the sender, since the sender makes most of the
> > performance-critical decisions (cwnd, pacing, TSO size, TSQ, etc).
> > From the sender-side the thing that would be most useful is to see
> > tp->snd_wnd, the receive window that the receiver has advertised to
> > the sender.
>
> This serves the purpose of adding an additional __u32 to avoid the
> would-be hole caused by the addition of the tcpi_rcvi_ooopack field.
>
> Signed-off-by: Thomas Higdon <[email protected]>
> ---
> changes from v3:
> - changed from rcv_wnd to snd_wnd
>
> include/uapi/linux/tcp.h | 1 +
> net/ipv4/tcp.c | 1 +
> 2 files changed, 2 insertions(+)
>
> diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
> index 20237987ccc8..240654f22d98 100644
> --- a/include/uapi/linux/tcp.h
> +++ b/include/uapi/linux/tcp.h
> @@ -272,6 +272,7 @@ struct tcp_info {
> __u32 tcpi_reord_seen; /* reordering events seen */
>
> __u32 tcpi_rcv_ooopack; /* Out-of-order packets received */
> + __u32 tcpi_snd_wnd; /* Remote peer's advertised recv window
> size */
> };
Thanks for adding this!
My run of ./scripts/checkpatch.pl is showing a warning on this line:
WARNING: line over 80 characters
#19: FILE: include/uapi/linux/tcp.h:273:
+ __u32 tcpi_snd_wnd; /* Remote peer's advertised recv
window size */
What if the comment is shortened up to fit in 80 columns and the units
(bytes) are added, something like:
__u32 tcpi_snd_wnd; /* peer's advertised recv window (bytes) */
neal
