tcp: increase tcp_limit_output_bytes default value to 4MB

Last change happened in 2018 with commit c73e5807e4f6
("tcp: tsq: no longer use limit_output_bytes for paced flows")

Modern NIC speeds got a 4x increase since then.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250513193919.1089692-10-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index b43222ee57cf9e54e38cb78f752f050c2f43a5cf..91b7d0a1c7fd884ee964d5be0d4dbd10ce040f76 100644 (file)
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -1099,7 +1099,7 @@ tcp_limit_output_bytes - INTEGER
        limits the number of bytes on qdisc or device to reduce artificial
        RTT/cwnd and reduce bufferbloat.
 
-       Default: 1048576 (16 * 65536)
+       Default: 4194304 (4 MB)
 
 tcp_challenge_ack_limit - INTEGER
        Limits number of Challenge ACK sent per second, as recommended

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index d5b5c32115d2ef84b0c91d43f584e571f342d9fb..6a14f9e6fef645511be5738e0ead22e168fb20b2 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -3495,8 +3495,8 @@ static int __net_init tcp_sk_init(struct net *net)
         * which are too large can cause TCP streams to be bursty.
         */
        net->ipv4.sysctl_tcp_tso_win_divisor = 3;
-       /* Default TSQ limit of 16 TSO segments */
-       net->ipv4.sysctl_tcp_limit_output_bytes = 16 * 65536;
+       /* Default TSQ limit of 4 MB */
+       net->ipv4.sysctl_tcp_limit_output_bytes = 4 << 20;
 
        /* rfc5961 challenge ack rate limiting, per net-ns, disabled by default. */
        net->ipv4.sysctl_tcp_challenge_ack_limit = INT_MAX;