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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

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.