Message ID | 20180426165810.164524-1-tracywwnj@gmail.com |
---|---|
State | Accepted, archived |
Delegated to: | David Miller |
Headers | show |
Series | [net-next] tcp: remove mss check in tcp_select_initial_window() | expand |
On Thu, Apr 26, 2018 at 12:58 PM Wei Wang <weiwan@google.com> wrote: > From: Wei Wang <weiwan@google.com> > In tcp_select_initial_window(), we only set rcv_wnd to > tcp_default_init_rwnd() if current mss > (1 << wscale). Otherwise, > rcv_wnd is kept at the full receive space of the socket which is a > value way larger than tcp_default_init_rwnd(). > With larger initial rcv_wnd value, receive buffer autotuning logic > takes longer to kick in and increase the receive buffer. > In a TCP throughput test where receiver has rmem[2] set to 125MB > (wscale is 11), we see the connection gets recvbuf limited at the > beginning of the connection and gets less throughput overall. > Signed-off-by: Wei Wang <weiwan@google.com> > Acked-by: Eric Dumazet <edumazet@google.com> > Acked-by: Soheil Hassas Yeganeh <soheil@google.com> > Acked-by: Yuchung Cheng <ycheng@google.com> > --- Acked-by: Neal Cardwell <ncardwell@google.com> Thanks, Wei! neal
From: Wei Wang <weiwan@google.com> Date: Thu, 26 Apr 2018 09:58:10 -0700 > From: Wei Wang <weiwan@google.com> > > In tcp_select_initial_window(), we only set rcv_wnd to > tcp_default_init_rwnd() if current mss > (1 << wscale). Otherwise, > rcv_wnd is kept at the full receive space of the socket which is a > value way larger than tcp_default_init_rwnd(). > With larger initial rcv_wnd value, receive buffer autotuning logic > takes longer to kick in and increase the receive buffer. > > In a TCP throughput test where receiver has rmem[2] set to 125MB > (wscale is 11), we see the connection gets recvbuf limited at the > beginning of the connection and gets less throughput overall. > > Signed-off-by: Wei Wang <weiwan@google.com> > Acked-by: Eric Dumazet <edumazet@google.com> > Acked-by: Soheil Hassas Yeganeh <soheil@google.com> > Acked-by: Yuchung Cheng <ycheng@google.com> Very nice commit message. Applied.
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 95feffb6d53f..d07c0dcc99aa 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -229,11 +229,9 @@ void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss, } } - if (mss > (1 << *rcv_wscale)) { - if (!init_rcv_wnd) /* Use default unless specified otherwise */ - init_rcv_wnd = tcp_default_init_rwnd(mss); - *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss); - } + if (!init_rcv_wnd) /* Use default unless specified otherwise */ + init_rcv_wnd = tcp_default_init_rwnd(mss); + *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss); /* Set the clamp no higher than max representable value */ (*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp);