tcp: increase tcp_rmem[2] to 32 MB

Last change to tcp_rmem[2] happened in 2012, in commit b49960a05e32
("tcp: change tcp_adv_win_scale and tcp_rmem[2]")

TCP performance on WAN is mostly limited by tcp_rmem[2] for receivers.

After this series improvements, it is time to increase the default.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250513193919.1089692-12-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 91b7d0a1c7fd884ee964d5be0d4dbd10ce040f76..0f1251cce31491930c3e446ae746e538d22fc5c7 100644 (file)
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -735,7 +735,7 @@ tcp_rmem - vector of 3 INTEGERs: min, default, max
        net.core.rmem_max.  Calling setsockopt() with SO_RCVBUF disables
        automatic tuning of that socket's receive buffer size, in which
        case this value is ignored.
-       Default: between 131072 and 6MB, depending on RAM size.
+       Default: between 131072 and 32MB, depending on RAM size.
 
 tcp_sack - BOOLEAN
        Enable select acknowledgments (SACKS).

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 0ae265d39184ed1a40a724a1ad6bb8f2f22d4fff..b7b6ab41b496f98bf82e099fab1da454dce1fe67 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -5231,7 +5231,7 @@ void __init tcp_init(void)
        /* Set per-socket limits to no more than 1/128 the pressure threshold */
        limit = nr_free_buffer_pages() << (PAGE_SHIFT - 7);
        max_wshare = min(4UL*1024*1024, limit);
-       max_rshare = min(6UL*1024*1024, limit);
+       max_rshare = min(32UL*1024*1024, limit);
 
        init_net.ipv4.sysctl_tcp_wmem[0] = PAGE_SIZE;
        init_net.ipv4.sysctl_tcp_wmem[1] = 16*1024;