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

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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
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. The maximum receive socket buffer size in bytes.
Default: 4194304
rps_default_mask rps_default_mask
---------------- ----------------
@@ -247,6 +249,8 @@ wmem_max
The maximum send socket buffer size in bytes. The maximum send socket buffer size in bytes.
Default: 4194304
message_burst and message_cost 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. 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, Exact value depends on architecture and kernel options,
but should be enough to allow queuing 256 packets 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. This value results in initial window of 65535.
max: maximal size of receive buffer allowed for automatically max: maximal size of receive buffer allowed for automatically
selected receiver buffers for TCP socket. This value does not override selected receiver buffers for TCP socket.
net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables Calling setsockopt() with SO_RCVBUF disables
automatic tuning of that socket's receive buffer size, in which automatic tuning of that socket's receive buffer size, in which
case this value is ignored. case this value is ignored.
Default: between 131072 and 32MB, depending on RAM size. 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_PACKETS 256
#define _SK_MEM_OVERHEAD SKB_TRUESIZE(256) #define _SK_MEM_OVERHEAD SKB_TRUESIZE(256)
#define SK_WMEM_MAX (_SK_MEM_OVERHEAD * _SK_MEM_PACKETS) #define SK_WMEM_DEFAULT (_SK_MEM_OVERHEAD * _SK_MEM_PACKETS)
#define SK_RMEM_MAX (_SK_MEM_OVERHEAD * _SK_MEM_PACKETS) #define SK_RMEM_DEFAULT (_SK_MEM_OVERHEAD * _SK_MEM_PACKETS)
extern __u32 sysctl_wmem_max; extern __u32 sysctl_wmem_max;
extern __u32 sysctl_rmem_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]; static struct lock_class_key af_kern_callback_keys[AF_MAX];
/* Run time adjustable parameters. */ /* 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); 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); EXPORT_SYMBOL(sysctl_rmem_max);
__u32 sysctl_wmem_default __read_mostly = SK_WMEM_MAX; __u32 sysctl_wmem_default __read_mostly = SK_WMEM_DEFAULT;
__u32 sysctl_rmem_default __read_mostly = SK_RMEM_MAX; __u32 sysctl_rmem_default __read_mostly = SK_RMEM_DEFAULT;
DEFINE_STATIC_KEY_FALSE(memalloc_socks_key); DEFINE_STATIC_KEY_FALSE(memalloc_socks_key);
EXPORT_SYMBOL_GPL(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_DELAY_PROBE_TIME] = 5 * HZ,
[NEIGH_VAR_INTERVAL_PROBE_TIME_MS] = 5 * HZ, [NEIGH_VAR_INTERVAL_PROBE_TIME_MS] = 5 * HZ,
[NEIGH_VAR_GC_STALETIME] = 60 * 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_PROXY_QLEN] = 64,
[NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ, [NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
[NEIGH_VAR_PROXY_DELAY] = (8 * HZ) / 10, [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_DELAY_PROBE_TIME] = 5 * HZ,
[NEIGH_VAR_INTERVAL_PROBE_TIME_MS] = 5 * HZ, [NEIGH_VAR_INTERVAL_PROBE_TIME_MS] = 5 * HZ,
[NEIGH_VAR_GC_STALETIME] = 60 * 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_PROXY_QLEN] = 64,
[NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ, [NEIGH_VAR_ANYCAST_DELAY] = 1 * HZ,
[NEIGH_VAR_PROXY_DELAY] = (8 * HZ) / 10, [NEIGH_VAR_PROXY_DELAY] = (8 * HZ) / 10,