[Beowulf] Kernel action relevant to us

Walid walid.shaari at gmail.com
Fri Aug 13 23:16:19 PDT 2010


Greg,

do we know if that have made it to any Linux Kernel?

kind regards

Walid

On 17 December 2009 05:05, Greg Lindahl <lindahl at pbm.com> wrote:

> The following patch, not yet accepted into the kernel, should allow
> local TCP connections to start up faster, while remote ones keep the
> same behavior of slow start.
>
> ----- Forwarded message from chavey at google.com -----
>
> From: chavey at google.com
> Date: Tue, 15 Dec 2009 13:15:28 -0800
> To: davem at davemloft.net
> CC: netdev at vger.kernel.org, therbert at google.com, chavey at google.com,
>        eric.dumazet at gmail.com
> Subject: [PATCH] Add rtnetlink init_rcvwnd to set the TCP initial receive
> window
> X-Mailing-List: netdev at vger.kernel.org
>
> Add rtnetlink init_rcvwnd to set the TCP initial receive window size
> advertised by passive and active TCP connections.
> The current Linux TCP implementation limits the advertised TCP initial
> receive window to the one prescribed by slow start. For short lived
> TCP connections used for transaction type of traffic (i.e. http
> requests), bounding the advertised TCP initial receive window results
> in increased latency to complete the transaction.
> Support for setting initial congestion window is already supported
> using rtnetlink init_cwnd, but the feature is useless without the
> ability to set a larger TCP initial receive window.
> The rtnetlink init_rcvwnd allows increasing the TCP initial receive
> window, allowing TCP connection to advertise larger TCP receive window
> than the ones bounded by slow start.
>
> Signed-off-by: Laurent Chavey <chavey at google.com>
> ---
>  include/linux/rtnetlink.h |    2 ++
>  include/net/dst.h         |    2 --
>  include/net/tcp.h         |    3 ++-
>  net/ipv4/syncookies.c     |    3 ++-
>  net/ipv4/tcp_output.c     |   17 +++++++++++++----
>  net/ipv6/syncookies.c     |    3 ++-
>  6 files changed, 21 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
> index adf2068..db6f614 100644
> --- a/include/linux/rtnetlink.h
> +++ b/include/linux/rtnetlink.h
> @@ -371,6 +371,8 @@ enum
>  #define RTAX_FEATURES RTAX_FEATURES
>        RTAX_RTO_MIN,
>  #define RTAX_RTO_MIN RTAX_RTO_MIN
> +       RTAX_INITRWND,
> +#define RTAX_INITRWND RTAX_INITRWND
>        __RTAX_MAX
>  };
>
> diff --git a/include/net/dst.h b/include/net/dst.h
> index 5a900dd..6ef812a 100644
> --- a/include/net/dst.h
> +++ b/include/net/dst.h
> @@ -84,8 +84,6 @@ struct dst_entry
>         * (L1_CACHE_SIZE would be too much)
>         */
>  #ifdef CONFIG_64BIT
> -       long                    __pad_to_align_refcnt[2];
> -#else
>        long                    __pad_to_align_refcnt[1];
>  #endif
>        /*
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 03a49c7..6f95d32 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -972,7 +972,8 @@ static inline void tcp_sack_reset(struct
> tcp_options_received *rx_opt)
>  /* Determine a window scaling and initial window to offer. */
>  extern void tcp_select_initial_window(int __space, __u32 mss,
>                                      __u32 *rcv_wnd, __u32 *window_clamp,
> -                                     int wscale_ok, __u8 *rcv_wscale);
> +                                     int wscale_ok, __u8 *rcv_wscale,
> +                                     __u32 init_rcv_wnd);
>
>  static inline int tcp_win_from_space(int space)
>  {
> diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
> index a6e0e07..d43173c 100644
> --- a/net/ipv4/syncookies.c
> +++ b/net/ipv4/syncookies.c
> @@ -356,7 +356,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct
> sk_buff *skb,
>
>        tcp_select_initial_window(tcp_full_space(sk), req->mss,
>                                  &req->rcv_wnd, &req->window_clamp,
> -                                 ireq->wscale_ok, &rcv_wscale);
> +                                 ireq->wscale_ok, &rcv_wscale,
> +                                 dst_metric(&rt->u.dst, RTAX_INITRWND));
>
>        ireq->rcv_wscale  = rcv_wscale;
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index fcd278a..ee42c75 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -179,7 +179,8 @@ static inline void tcp_event_ack_sent(struct sock *sk,
> unsigned int pkts)
>  */
>  void tcp_select_initial_window(int __space, __u32 mss,
>                               __u32 *rcv_wnd, __u32 *window_clamp,
> -                              int wscale_ok, __u8 *rcv_wscale)
> +                              int wscale_ok, __u8 *rcv_wscale,
> +                              __u32 init_rcv_wnd)
>  {
>        unsigned int space = (__space < 0 ? 0 : __space);
>
> @@ -228,7 +229,13 @@ void tcp_select_initial_window(int __space, __u32 mss,
>                        init_cwnd = 2;
>                else if (mss > 1460)
>                        init_cwnd = 3;
> -               if (*rcv_wnd > init_cwnd * mss)
> +               /* when initializing use the value from init_rcv_wnd
> +                * rather than the default from above
> +                */
> +               if (init_rcv_wnd &&
> +                   (*rcv_wnd > init_rcv_wnd * mss))
> +                       *rcv_wnd = init_rcv_wnd * mss;
> +               else if (*rcv_wnd > init_cwnd * mss)
>                        *rcv_wnd = init_cwnd * mss;
>        }
>
> @@ -2254,7 +2261,8 @@ struct sk_buff *tcp_make_synack(struct sock *sk,
> struct dst_entry *dst,
>                        &req->rcv_wnd,
>                        &req->window_clamp,
>                        ireq->wscale_ok,
> -                       &rcv_wscale);
> +                       &rcv_wscale,
> +                       dst_metric(dst, RTAX_INITRWND));
>                ireq->rcv_wscale = rcv_wscale;
>        }
>
> @@ -2342,7 +2350,8 @@ static void tcp_connect_init(struct sock *sk)
>                                  &tp->rcv_wnd,
>                                  &tp->window_clamp,
>                                  sysctl_tcp_window_scaling,
> -                                 &rcv_wscale);
> +                                 &rcv_wscale,
> +                                 dst_metric(dst, RTAX_INITRWND));
>
>        tp->rx_opt.rcv_wscale = rcv_wscale;
>        tp->rcv_ssthresh = tp->rcv_wnd;
> diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
> index 6b6ae91..c8982aa 100644
> --- a/net/ipv6/syncookies.c
> +++ b/net/ipv6/syncookies.c
> @@ -267,7 +267,8 @@ struct sock *cookie_v6_check(struct sock *sk, struct
> sk_buff *skb)
>        req->window_clamp = tp->window_clamp ? :dst_metric(dst,
> RTAX_WINDOW);
>        tcp_select_initial_window(tcp_full_space(sk), req->mss,
>                                  &req->rcv_wnd, &req->window_clamp,
> -                                 ireq->wscale_ok, &rcv_wscale);
> +                                 ireq->wscale_ok, &rcv_wscale,
> +                                 dst_metric(dst, RTAX_INITRWND));
>
>        ireq->rcv_wscale = rcv_wscale;
>
> --
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