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