Documentation / networking / smc-sysctl.rst


Based on kernel version 6.10. Page generated on 2024-07-16 09:00 EST.

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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 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: 64KiB

rmem - INTEGER
	Initial size of receive buffer (RMB) used by SMC sockets.

	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: 64KiB

smcr_max_links_per_lgr - INTEGER
	Controls the max number of links can be added to a SMC-R link group. Notice that
	the actual number of the links added to a SMC-R link group depends on the number
	of RDMA devices exist in the system. The acceptable value ranges from 1 to 2. Only
	for SMC-R v2.1 and later.

	Default: 2

smcr_max_conns_per_lgr - INTEGER
	Controls the max number of connections can be added to a SMC-R link group. The
	acceptable value ranges from 16 to 255. Only for SMC-R v2.1 and later.

	Default: 255