This patch gets rid of the tcp_default_win_scale sysctl and instead
computes the optimum maximum window scale. It just means one less
thing to have to tune. I also moved the code out of the inline because
it gets called three places and isn't in the critical path.
As a side effect, it will cause a smaller window scale for many people
since the default tcp_rmem fits in a win_scale of 2. This is allows for
finer grain windows (good), but may mask some of the problems with bad
implementations we have already seen (bad).
Signed-off-by: Stephen Hemminger <shemminger@xxxxxxxx>
diff -Nru a/include/net/tcp.h b/include/net/tcp.h
--- a/include/net/tcp.h 2004-08-26 13:03:22 -07:00
+++ b/include/net/tcp.h 2004-08-26 13:03:22 -07:00
@@ -611,7 +611,6 @@
extern int sysctl_tcp_bic;
extern int sysctl_tcp_bic_fast_convergence;
extern int sysctl_tcp_bic_low_window;
-extern int sysctl_tcp_default_win_scale;
extern int sysctl_tcp_moderate_rcvbuf;
extern atomic_t tcp_memory_allocated;
@@ -1690,68 +1689,10 @@
*ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_WINDOW << 16) |
(TCPOLEN_WINDOW << 8) | (wscale));
}
-/* Determine a window scaling and initial window to offer.
- * Based on the assumption that the given amount of space
- * will be offered. Store the results in the tp structure.
- * NOTE: for smooth operation initial space offering should
- * be a multiple of mss if possible. We assume here that mss >= 1.
- * This MUST be enforced by all callers.
- */
-static inline void tcp_select_initial_window(int __space, __u32 mss,
- __u32 *rcv_wnd,
- __u32 *window_clamp,
- int wscale_ok,
- __u8 *rcv_wscale)
-{
- unsigned int space = (__space < 0 ? 0 : __space);
-
- /* If no clamp set the clamp to the max possible scaled window */
- if (*window_clamp == 0)
- (*window_clamp) = (65535 << 14);
- space = min(*window_clamp, space);
-
- /* Quantize space offering to a multiple of mss if possible. */
- if (space > mss)
- space = (space / mss) * mss;
-
- /* NOTE: offering an initial window larger than 32767
- * will break some buggy TCP stacks. We try to be nice.
- * If we are not window scaling, then this truncates
- * our initial window offering to 32k. There should also
- * be a sysctl option to stop being nice.
- */
- (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
- (*rcv_wscale) = 0;
- if (wscale_ok) {
- /* See RFC1323 for an explanation of the limit to 14 */
- while (space > 65535 && (*rcv_wscale) < 14) {
- space >>= 1;
- (*rcv_wscale)++;
- }
- if (*rcv_wscale && sysctl_tcp_app_win && space>=mss &&
- space - max((space>>sysctl_tcp_app_win), mss>>*rcv_wscale)
< 65536/2)
- (*rcv_wscale)--;
-
- *rcv_wscale = max((__u8)sysctl_tcp_default_win_scale,
- *rcv_wscale);
- }
-
- /* Set initial window to value enough for senders,
- * following RFC1414. Senders, not following this RFC,
- * will be satisfied with 2.
- */
- if (mss > (1<<*rcv_wscale)) {
- int init_cwnd = 4;
- if (mss > 1460*3)
- init_cwnd = 2;
- else if (mss > 1460)
- init_cwnd = 3;
- if (*rcv_wnd > init_cwnd*mss)
- *rcv_wnd = init_cwnd*mss;
- }
- /* Set the clamp no higher than max representable value */
- (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
-}
+/* 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);
static inline int tcp_win_from_space(int space)
{
@@ -1761,13 +1702,13 @@
}
/* Note: caller must be prepared to deal with negative returns */
-static inline int tcp_space(struct sock *sk)
+static inline int tcp_space(const struct sock *sk)
{
return tcp_win_from_space(sk->sk_rcvbuf -
atomic_read(&sk->sk_rmem_alloc));
}
-static inline int tcp_full_space( struct sock *sk)
+static inline int tcp_full_space(const struct sock *sk)
{
return tcp_win_from_space(sk->sk_rcvbuf);
}
diff -Nru a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
--- a/net/ipv4/sysctl_net_ipv4.c 2004-08-26 13:03:22 -07:00
+++ b/net/ipv4/sysctl_net_ipv4.c 2004-08-26 13:03:22 -07:00
@@ -667,14 +667,6 @@
.proc_handler = &proc_dointvec,
},
{
- .ctl_name = NET_TCP_DEFAULT_WIN_SCALE,
- .procname = "tcp_default_win_scale",
- .data = &sysctl_tcp_default_win_scale,
- .maxlen = sizeof(int),
- .mode = 0644,
- .proc_handler = &proc_dointvec,
- },
- {
.ctl_name = NET_TCP_MODERATE_RCVBUF,
.procname = "tcp_moderate_rcvbuf",
.data = &sysctl_tcp_moderate_rcvbuf,
diff -Nru a/net/ipv4/tcp.c b/net/ipv4/tcp.c
--- a/net/ipv4/tcp.c 2004-08-26 13:03:22 -07:00
+++ b/net/ipv4/tcp.c 2004-08-26 13:03:22 -07:00
@@ -276,8 +276,6 @@
atomic_t tcp_orphan_count = ATOMIC_INIT(0);
-int sysctl_tcp_default_win_scale = 7;
-
int sysctl_tcp_mem[3];
int sysctl_tcp_wmem[3] = { 4 * 1024, 16 * 1024, 128 * 1024 };
int sysctl_tcp_rmem[3] = { 4 * 1024, 87380, 87380 * 2 };
diff -Nru a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
--- a/net/ipv4/tcp_output.c 2004-08-26 13:03:22 -07:00
+++ b/net/ipv4/tcp_output.c 2004-08-26 13:03:22 -07:00
@@ -143,6 +143,65 @@
tcp_clear_xmit_timer(sk, TCP_TIME_DACK);
}
+/* Determine a window scaling and initial window to offer.
+ * Based on the assumption that the given amount of space
+ * will be offered. Store the results in the tp structure.
+ * NOTE: for smooth operation initial space offering should
+ * be a multiple of mss if possible. We assume here that mss >= 1.
+ * This MUST be enforced by all callers.
+ */
+void tcp_select_initial_window(int __space, __u32 mss,
+ __u32 *rcv_wnd, __u32 *window_clamp,
+ int wscale_ok, __u8 *rcv_wscale)
+{
+ unsigned int space = (__space < 0 ? 0 : __space);
+
+ /* If no clamp set the clamp to the max possible scaled window */
+ if (*window_clamp == 0)
+ (*window_clamp) = (65535 << 14);
+ space = min(*window_clamp, space);
+
+ /* Quantize space offering to a multiple of mss if possible. */
+ if (space > mss)
+ space = (space / mss) * mss;
+
+ /* NOTE: offering an initial window larger than 32767
+ * will break some buggy TCP stacks. We try to be nice.
+ * If we are not window scaling, then this truncates
+ * our initial window offering to 32k. There should also
+ * be a sysctl option to stop being nice.
+ */
+ (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
+ (*rcv_wscale) = 0;
+ if (wscale_ok) {
+ /* Set window scaling on max possible window
+ * See RFC1323 for an explanation of the limit to 14
+ */
+ space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
+ while (space > 65535 && (*rcv_wscale) < 14) {
+ space >>= 1;
+ (*rcv_wscale)++;
+ }
+ }
+
+ /* Set initial window to value enough for senders,
+ * following RFC1414. Senders, not following this RFC,
+ * will be satisfied with 2.
+ */
+ if (mss > (1<<*rcv_wscale)) {
+ int init_cwnd = 4;
+ if (mss > 1460*3)
+ init_cwnd = 2;
+ else if (mss > 1460)
+ init_cwnd = 3;
+ if (*rcv_wnd > init_cwnd*mss)
+ *rcv_wnd = init_cwnd*mss;
+ }
+
+ /* Set the clamp no higher than max representable value */
+ (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
+}
+
/* Chose a new window to advertise, update state in tcp_opt for the
* socket, and return result with RFC1323 scaling applied. The return
* value can be stuffed directly into th->window for an outgoing
|