On Fri, Sep 13, 2019 at 2:02 PM Neal Cardwell <ncardw...@google.com> wrote:
>
> On Fri, Sep 13, 2019 at 3:36 PM Thomas Higdon <t...@fb.com> 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 <t...@fb.com>
> > ---
> > 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)
> */
just a thought: will tcpi_peer_rcv_wnd be more self-explanatory?
>
> neal
