linuxdebug/Documentation/networking/smc-sysctl.rst

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.. SPDX-License-Identifier: GPL-2.0
==========
SMC Sysctl
==========
/proc/sys/net/smc/* Variables
=============================
autocorking_size - INTEGER
Setting SMC auto corking size:
SMC auto corking is like TCP auto corking from the application's
perspective of view. When applications do consecutive small
write()/sendmsg() system calls, we try to coalesce these small writes
as much as possible, to lower total amount of CDC and RDMA Write been
sent.
autocorking_size limits the maximum corked bytes that can be sent to
the under device in 1 single sending. If set to 0, the SMC auto corking
is disabled.
Applications can still use TCP_CORK for optimal behavior when they
know how/when to uncork their sockets.
Default: 64K
smcr_buf_type - INTEGER
Controls which type of sndbufs and RMBs to use in later newly created
SMC-R link group. Only for SMC-R.
Default: 0 (physically contiguous sndbufs and RMBs)
Possible values:
- 0 - Use physically contiguous buffers
- 1 - Use virtually contiguous buffers
- 2 - Mixed use of the two types. Try physically contiguous buffers first.
If not available, use virtually contiguous buffers then.
smcr_testlink_time - INTEGER
How frequently SMC-R link sends out TEST_LINK LLC messages to confirm
viability, after the last activity of connections on it. Value 0 means
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