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Date: Sat, 29 Oct 2011 00:14:03 +0300
From: Daniel Baluta <dbaluta@...acom.com>
To: davem@...emloft.net, eric.dumazet@...il.com
Cc: kuznet@....inr.ac.ru, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
kaber@...sh.net, netdev@...r.kernel.org, luto@...capital.net,
rick.jones2@...com, Daniel Baluta <dbaluta@...acom.com>
Subject: [RFC v2] tcp: Export TCP Delayed ACK parameters to user
RFC2581 ($4.2) specifies when an ACK should be generated as follows:
" .. an ACK SHOULD be generated for at least every second
full-sized segment, and MUST be generated within 500 ms
of the arrival of the first unacknowledged packet.
"
We export the number of segments and the timeout limits
specified above, so that a user can tune them according
to its needs.
Specifically:
* /proc/sys/net/ipv4/tcp_delack_segs, represents
the threshold for the number of segments.
* /proc/sys/net/ipv4/tcp_delack_min, specifies
the minimum timeout value
* /proc/sys/net/ipv4/tcp_delack_max, specifies
the maximum timeout value.
Signed-off-by: Daniel Baluta <dbaluta@...acom.com>
---
Changes since v1:
* added documentation for newly introduced /proc entries.
* exported symbols sysctl_tcp_delack_{min|max}.
* removed TCP_DELACK_{MIN|MAX} and used directly
sysctl_tcp_delack{min|max}.
* renamed tcp_snd_thresh to tcp_delack_thresh.
* added const qualifier to struct sock *sk.
---
Documentation/networking/ip-sysctl.txt | 13 +++++++++++++
include/net/tcp.h | 18 +++++++++++++++---
net/dccp/output.c | 2 +-
net/dccp/timer.c | 2 +-
net/ipv4/sysctl_net_ipv4.c | 21 +++++++++++++++++++++
net/ipv4/tcp.c | 5 +++--
net/ipv4/tcp_input.c | 8 +++++---
net/ipv4/tcp_output.c | 13 +++++++++----
net/ipv4/tcp_timer.c | 3 ++-
9 files changed, 70 insertions(+), 15 deletions(-)
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index cb7f314..efbd1b4 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -524,6 +524,19 @@ tcp_thin_dupack - BOOLEAN
Documentation/networking/tcp-thin.txt
Default: 0
+tcp_delack_segs: - INTEGER
+ Sets the strict minimal number of full-sized TCP segments
+ received after which an ACK should be sent.
+ Default: 1 (as specified in RFC2582, S4.2)
+
+tcp_delack_min: - INTEGER
+ Sets the minimum time (in miliseconds) to delay before sending an ACK.
+ Default: 40ms
+
+tcp_delack_max: - INTEGER
+ Sets the maximum time (in miliseconds) to delay before sending an ACK.
+ Default: 200ms
+
UDP variables:
udp_mem - vector of 3 INTEGERs: min, pressure, max
diff --git a/include/net/tcp.h b/include/net/tcp.h
index e147f42..9e29a9d 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -111,14 +111,18 @@ extern void tcp_time_wait(struct sock *sk, int state, int timeo);
* TIME-WAIT timer.
*/
-#define TCP_DELACK_MAX ((unsigned)(HZ/5)) /* maximal time to delay before sending an ACK */
+/* default maximum time to delay before sending an ACK */
+#define TCP_DELACK_MAX_DEFAULT ((unsigned)(HZ/5))
+
#if HZ >= 100
-#define TCP_DELACK_MIN ((unsigned)(HZ/25)) /* minimal time to delay before sending an ACK */
+/* default minimum time to delay before sending an ACK */
+#define TCP_DELACK_MIN_DEFAULT ((unsigned)(HZ/25))
#define TCP_ATO_MIN ((unsigned)(HZ/25))
#else
-#define TCP_DELACK_MIN 4U
+#define TCP_DELACK_MIN_DEFAULT 4U
#define TCP_ATO_MIN 4U
#endif
+
#define TCP_RTO_MAX ((unsigned)(120*HZ))
#define TCP_RTO_MIN ((unsigned)(HZ/5))
#define TCP_TIMEOUT_INIT ((unsigned)(1*HZ)) /* RFC2988bis initial RTO value */
@@ -251,6 +255,9 @@ extern int sysctl_tcp_max_ssthresh;
extern int sysctl_tcp_cookie_size;
extern int sysctl_tcp_thin_linear_timeouts;
extern int sysctl_tcp_thin_dupack;
+extern int sysctl_tcp_delack_segs;
+extern int sysctl_tcp_delack_min;
+extern int sysctl_tcp_delack_max;
extern atomic_long_t tcp_memory_allocated;
extern struct percpu_counter tcp_sockets_allocated;
@@ -1558,6 +1565,11 @@ static inline struct tcp_extend_values *tcp_xv(struct request_values *rvp)
return (struct tcp_extend_values *)rvp;
}
+static inline int tcp_delack_thresh(const struct sock *sk)
+{
+ return inet_csk(sk)->icsk_ack.rcv_mss * sysctl_tcp_delack_segs;
+}
+
extern void tcp_v4_init(void);
extern void tcp_init(void);
diff --git a/net/dccp/output.c b/net/dccp/output.c
index dede3ed..9b5b0c4 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -577,7 +577,7 @@ void dccp_send_ack(struct sock *sk)
inet_csk_schedule_ack(sk);
inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
- TCP_DELACK_MAX,
+ sysctl_tcp_delack_max,
DCCP_RTO_MAX);
return;
}
diff --git a/net/dccp/timer.c b/net/dccp/timer.c
index 7587870..7bae11e 100644
--- a/net/dccp/timer.c
+++ b/net/dccp/timer.c
@@ -202,7 +202,7 @@ static void dccp_delack_timer(unsigned long data)
icsk->icsk_ack.blocked = 1;
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
sk_reset_timer(sk, &icsk->icsk_delack_timer,
- jiffies + TCP_DELACK_MIN);
+ jiffies + sysctl_tcp_delack_min);
goto out;
}
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 69fd720..c22c4c5 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -639,6 +639,27 @@ static struct ctl_table ipv4_table[] = {
.proc_handler = proc_dointvec
},
{
+ .procname = "tcp_delack_segs",
+ .data = &sysctl_tcp_delack_segs,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec
+ },
+ {
+ .procname = "tcp_delack_min",
+ .data = &sysctl_tcp_delack_min,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_ms_jiffies
+ },
+ {
+ .procname = "tcp_delack_max",
+ .data = &sysctl_tcp_delack_max,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_ms_jiffies
+ },
+ {
.procname = "udp_mem",
.data = &sysctl_udp_mem,
.maxlen = sizeof(sysctl_udp_mem),
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 34f5db1..731e284 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1204,8 +1204,9 @@ void tcp_cleanup_rbuf(struct sock *sk, int copied)
/* Delayed ACKs frequently hit locked sockets during bulk
* receive. */
if (icsk->icsk_ack.blocked ||
- /* Once-per-two-segments ACK was not sent by tcp_input.c */
- tp->rcv_nxt - tp->rcv_wup > icsk->icsk_ack.rcv_mss ||
+ /* More than once-per-tcp_delack_segs-segments ACK
+ * was not sent by tcp_input.c */
+ tp->rcv_nxt - tp->rcv_wup > tcp_delack_thresh(sk) ||
/*
* If this read emptied read buffer, we send ACK, if
* connection is not bidirectional, user drained
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 52b5c2d..f2893a9 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -98,6 +98,8 @@ int sysctl_tcp_thin_dupack __read_mostly;
int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
int sysctl_tcp_abc __read_mostly;
+int sysctl_tcp_delack_segs __read_mostly = 1;
+
#define FLAG_DATA 0x01 /* Incoming frame contained data. */
#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
@@ -4993,8 +4995,8 @@ static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
{
struct tcp_sock *tp = tcp_sk(sk);
- /* More than one full frame received... */
- if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss &&
+ /* More than tcp_delack_segs full frame(s) received... */
+ if (((tp->rcv_nxt - tp->rcv_wup) > tcp_delack_thresh(sk) &&
/* ... and right edge of window advances far enough.
* (tcp_recvmsg() will send ACK otherwise). Or...
*/
@@ -5689,7 +5691,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
tcp_incr_quickack(sk);
tcp_enter_quickack_mode(sk);
inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
- TCP_DELACK_MAX, TCP_RTO_MAX);
+ sysctl_tcp_delack_max, TCP_RTO_MAX);
discard:
__kfree_skb(skb);
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 980b98f..f4e7614 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -63,6 +63,11 @@ int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
int sysctl_tcp_cookie_size __read_mostly = 0; /* TCP_COOKIE_MAX */
EXPORT_SYMBOL_GPL(sysctl_tcp_cookie_size);
+int sysctl_tcp_delack_min __read_mostly = TCP_DELACK_MIN_DEFAULT;
+EXPORT_SYMBOL(sysctl_tcp_delack_min);
+
+int sysctl_tcp_delack_max __read_mostly = TCP_DELACK_MAX_DEFAULT;
+EXPORT_SYMBOL(sysctl_tcp_delack_max);
/* Account for new data that has been sent to the network. */
static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb)
@@ -2670,13 +2675,13 @@ void tcp_send_delayed_ack(struct sock *sk)
int ato = icsk->icsk_ack.ato;
unsigned long timeout;
- if (ato > TCP_DELACK_MIN) {
+ if (ato > sysctl_tcp_delack_min) {
const struct tcp_sock *tp = tcp_sk(sk);
int max_ato = HZ / 2;
if (icsk->icsk_ack.pingpong ||
(icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
- max_ato = TCP_DELACK_MAX;
+ max_ato = sysctl_tcp_delack_max;
/* Slow path, intersegment interval is "high". */
@@ -2685,7 +2690,7 @@ void tcp_send_delayed_ack(struct sock *sk)
* directly.
*/
if (tp->srtt) {
- int rtt = max(tp->srtt >> 3, TCP_DELACK_MIN);
+ int rtt = max_t(unsigned, tp->srtt >> 3, sysctl_tcp_delack_min);
if (rtt < max_ato)
max_ato = rtt;
@@ -2734,7 +2739,7 @@ void tcp_send_ack(struct sock *sk)
inet_csk_schedule_ack(sk);
inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
- TCP_DELACK_MAX, TCP_RTO_MAX);
+ sysctl_tcp_delack_max, TCP_RTO_MAX);
return;
}
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 2e0f0af..1bdc1c4 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -219,7 +219,8 @@ static void tcp_delack_timer(unsigned long data)
/* Try again later. */
icsk->icsk_ack.blocked = 1;
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
- sk_reset_timer(sk, &icsk->icsk_delack_timer, jiffies + TCP_DELACK_MIN);
+ sk_reset_timer(sk, &icsk->icsk_delack_timer,
+ jiffies + sysctl_tcp_delack_min);
goto out_unlock;
}
--
1.7.2.5
--
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