net/smc: Unbind r/w buffer size from clcsock and make them tunable

Currently, SMC uses smc->sk.sk_{rcv|snd}buf to create buffers for
send buffer and RMB. And the values of buffer size are from tcp_{w|r}mem
in clcsock.

The buffer size from TCP socket doesn't fit SMC well. Generally, buffers
are usually larger than TCP for SMC-R/-D to get higher performance, for
they are different underlay devices and paths.

So this patch unbinds buffer size from TCP, and introduces two sysctl
knobs to tune them independently. Also, these knobs are per net
namespace and work for containers.

Signed-off-by: Tony Lu <tonylu@linux.alibaba.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/Documentation/networking/smc-sysctl.rst b/Documentation/networking/smc-sysctl.rst
index 45ba1522e189..6d8acdbe9be1 100644
--- a/Documentation/networking/smc-sysctl.rst
+++ b/Documentation/networking/smc-sysctl.rst
@@ -41,3 +41,21 @@ smcr_testlink_time - INTEGER
 	disabling TEST_LINK.
 
 	Default: 30 seconds.
+
+wmem - INTEGER
+	Initial size of send buffer used by SMC sockets.
+	The default value inherits from net.ipv4.tcp_wmem[1].
+
+	The minimum value is 16KiB and there is no hard limit for max value, but
+	only allowed 512KiB for SMC-R and 1MiB for SMC-D.
+
+	Default: 16K
+
+rmem - INTEGER
+	Initial size of receive buffer (RMB) used by SMC sockets.
+	The default value inherits from net.ipv4.tcp_rmem[1].
+
+	The minimum value is 16KiB and there is no hard limit for max value, but
+	only allowed 512KiB for SMC-R and 1MiB for SMC-D.
+
+	Default: 128K