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net: set net.core.rmem_max and net.core.wmem_max to 4 MB 

SO_RCVBUF and SO_SNDBUF have limited range today, unless
distros or system admins change rmem_max and wmem_max.

Even iproute2 uses 1 MB SO_RCVBUF which is capped by
the kernel.

Decouple [rw]mem_max and [rw]mem_default and increase
[rw]mem_max to 4 MB.

Before:

$ sysctl net.core.rmem_default net.core.rmem_max net.core.wmem_default net.core.wmem_max
net.core.rmem_default = 212992
net.core.rmem_max = 212992
net.core.wmem_default = 212992
net.core.wmem_max = 212992

After:

$ sysctl net.core.rmem_default net.core.rmem_max net.core.wmem_default net.core.wmem_max
net.core.rmem_default = 212992
net.core.rmem_max = 4194304
net.core.wmem_default = 212992
net.core.wmem_max = 4194304

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Link: https://patch.msgid.link/20250819174030.1986278-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2025-08-19 17:40:30 +00:00 committed by Jakub Kicinski
parent 2a2e6e5375
commit a6d4f25888
6 changed files with 15 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
Documentation/admin-guide/sysctl/net.rst
View File

@ -222,6 +222,8 @@ rmem_max
The maximum receive socket buffer size in bytes.
Default: 4194304
rps_default_mask
----------------
@ -247,6 +249,8 @@ wmem_max
The maximum send socket buffer size in bytes.
Default: 4194304
message_burst and message_cost
------------------------------

6
Documentation/networking/ip-sysctl.rst
View File

@ -209,7 +209,7 @@ neigh/default/unres_qlen_bytes - INTEGER
Setting negative value is meaningless and will return error.
Default: SK_WMEM_MAX, (same as net.core.wmem_default).
Default: SK_WMEM_DEFAULT, (same as net.core.wmem_default).
Exact value depends on architecture and kernel options,
but should be enough to allow queuing 256 packets
@ -805,8 +805,8 @@ tcp_rmem - vector of 3 INTEGERs: min, default, max
This value results in initial window of 65535.
max: maximal size of receive buffer allowed for automatically
selected receiver buffers for TCP socket. This value does not override
net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables
selected receiver buffers for TCP socket.
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 32MB, depending on RAM size.

4
include/net/sock.h
View File

@ -2970,8 +2970,8 @@ void sk_get_meminfo(const struct sock *sk, u32 *meminfo);
*/
#define _SK_MEM_PACKETS 256
#define _SK_MEM_OVERHEAD SKB_TRUESIZE(256)
#define SK_WMEM_MAX (_SK_MEM_OVERHEAD * _SK_MEM_PACKETS)
#define SK_RMEM_MAX (_SK_MEM_OVERHEAD * _SK_MEM_PACKETS)
#define SK_WMEM_DEFAULT (_SK_MEM_OVERHEAD * _SK_MEM_PACKETS)
#define SK_RMEM_DEFAULT (_SK_MEM_OVERHEAD * _SK_MEM_PACKETS)
extern __u32 sysctl_wmem_max;
extern __u32 sysctl_rmem_max;

8
net/core/sock.c
View File

@ -281,12 +281,12 @@ static struct lock_class_key af_elock_keys[AF_MAX];
static struct lock_class_key af_kern_callback_keys[AF_MAX];
/* Run time adjustable parameters. */
__u32 sysctl_wmem_max __read_mostly = SK_WMEM_MAX;
__u32 sysctl_wmem_max __read_mostly = 4 << 20;
EXPORT_SYMBOL(sysctl_wmem_max);
__u32 sysctl_rmem_max __read_mostly = SK_RMEM_MAX;
__u32 sysctl_rmem_max __read_mostly = 4 << 20;
EXPORT_SYMBOL(sysctl_rmem_max);
__u32 sysctl_wmem_default __read_mostly = SK_WMEM_MAX;
__u32 sysctl_rmem_default __read_mostly = SK_RMEM_MAX;
__u32 sysctl_wmem_default __read_mostly = SK_WMEM_DEFAULT;
__u32 sysctl_rmem_default __read_mostly = SK_RMEM_DEFAULT;
DEFINE_STATIC_KEY_FALSE(memalloc_socks_key);
EXPORT_SYMBOL_GPL(memalloc_socks_key);

2
net/ipv4/arp.c
View File

@ -170,7 +170,7 @@ struct neigh_table arp_tbl = {
[NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
[NEIGH_VAR_INTERVAL_PROBE_TIME_MS] = 5 * HZ,
[NEIGH_VAR_GC_STALETIME] = 60 * HZ,
[NEIGH_VAR_QUEUE_LEN_BYTES] = SK_WMEM_MAX,
[NEIGH_VAR_QUEUE_LEN_BYTES] = SK_WMEM_DEFAULT,
[NEIGH_VAR_PROXY_QLEN] = 64,
[NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
[NEIGH_VAR_PROXY_DELAY] = (8 * HZ) / 10,

2
net/ipv6/ndisc.c
View File

@ -130,7 +130,7 @@ struct neigh_table nd_tbl = {
[NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
[NEIGH_VAR_INTERVAL_PROBE_TIME_MS] = 5 * HZ,
[NEIGH_VAR_GC_STALETIME] = 60 * HZ,
[NEIGH_VAR_QUEUE_LEN_BYTES] = SK_WMEM_MAX,
[NEIGH_VAR_QUEUE_LEN_BYTES] = SK_WMEM_DEFAULT,
[NEIGH_VAR_PROXY_QLEN] = 64,
[NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
[NEIGH_VAR_PROXY_DELAY] = (8 * HZ) / 10,