1.. SPDX-License-Identifier: GPL-2.0 2 3========== 4SMC Sysctl 5========== 6 7/proc/sys/net/smc/* Variables 8============================= 9 10autocorking_size - INTEGER 11 Setting SMC auto corking size: 12 SMC auto corking is like TCP auto corking from the application's 13 perspective of view. When applications do consecutive small 14 write()/sendmsg() system calls, we try to coalesce these small writes 15 as much as possible, to lower total amount of CDC and RDMA Write been 16 sent. 17 autocorking_size limits the maximum corked bytes that can be sent to 18 the under device in 1 single sending. If set to 0, the SMC auto corking 19 is disabled. 20 Applications can still use TCP_CORK for optimal behavior when they 21 know how/when to uncork their sockets. 22 23 Default: 64K 24 25smcr_buf_type - INTEGER 26 Controls which type of sndbufs and RMBs to use in later newly created 27 SMC-R link group. Only for SMC-R. 28 29 Default: 0 (physically contiguous sndbufs and RMBs) 30 31 Possible values: 32 33 - 0 - Use physically contiguous buffers 34 - 1 - Use virtually contiguous buffers 35 - 2 - Mixed use of the two types. Try physically contiguous buffers first. 36 If not available, use virtually contiguous buffers then. 37 38smcr_testlink_time - INTEGER 39 How frequently SMC-R link sends out TEST_LINK LLC messages to confirm 40 viability, after the last activity of connections on it. Value 0 means 41 disabling TEST_LINK. 42 43 Default: 30 seconds. 44 45wmem - INTEGER 46 Initial size of send buffer used by SMC sockets. 47 48 The minimum value is 16KiB and there is no hard limit for max value, but 49 only allowed 512KiB for SMC-R and 1MiB for SMC-D. 50 51 Default: 64KiB 52 53rmem - INTEGER 54 Initial size of receive buffer (RMB) used by SMC sockets. 55 56 The minimum value is 16KiB and there is no hard limit for max value, but 57 only allowed 512KiB for SMC-R and 1MiB for SMC-D. 58 59 Default: 64KiB 60 61smcr_max_links_per_lgr - INTEGER 62 Controls the max number of links can be added to a SMC-R link group. Notice that 63 the actual number of the links added to a SMC-R link group depends on the number 64 of RDMA devices exist in the system. The acceptable value ranges from 1 to 2. Only 65 for SMC-R v2.1 and later. 66 67 Default: 2 68 69smcr_max_conns_per_lgr - INTEGER 70 Controls the max number of connections can be added to a SMC-R link group. The 71 acceptable value ranges from 16 to 255. Only for SMC-R v2.1 and later. 72 73 Default: 255 74 75smcr_max_send_wr - INTEGER 76 So-called work request buffers are SMCR link (and RDMA queue pair) level 77 resources necessary for performing RDMA operations. Since up to 255 78 connections can share a link group and thus also a link and the number 79 of the work request buffers is decided when the link is allocated, 80 depending on the workload it can be a bottleneck in a sense that threads 81 have to wait for work request buffers to become available. Before the 82 introduction of this control the maximal number of work request buffers 83 available on the send path used to be hard coded to 16. With this control 84 it becomes configurable. The acceptable range is between 2 and 2048. 85 86 Please be aware that all the buffers need to be allocated as a physically 87 continuous array in which each element is a single buffer and has the size 88 of SMC_WR_BUF_SIZE (48) bytes. If the allocation fails, we keep retrying 89 with half of the buffer count until it is ether successful or (unlikely) 90 we dip below the old hard coded value which is 16 where we give up much 91 like before having this control. 92 93 Default: 16 94 95smcr_max_recv_wr - INTEGER 96 So-called work request buffers are SMCR link (and RDMA queue pair) level 97 resources necessary for performing RDMA operations. Since up to 255 98 connections can share a link group and thus also a link and the number 99 of the work request buffers is decided when the link is allocated, 100 depending on the workload it can be a bottleneck in a sense that threads 101 have to wait for work request buffers to become available. Before the 102 introduction of this control the maximal number of work request buffers 103 available on the receive path used to be hard coded to 16. With this control 104 it becomes configurable. The acceptable range is between 2 and 2048. 105 106 Please be aware that all the buffers need to be allocated as a physically 107 continuous array in which each element is a single buffer and has the size 108 of SMC_WR_BUF_SIZE (48) bytes. If the allocation fails, we keep retrying 109 with half of the buffer count until it is ether successful or (unlikely) 110 we dip below the old hard coded value which is 16 where we give up much 111 like before having this control. 112 113 Default: 48 114 115limit_smc_hs - INTEGER 116 Whether to limit SMC handshake for newly created sockets. 117 118 When enabled, SMC listen path applies handshake limitation based on 119 handshake worker congestion and queued SMC handshake load. 120 121 Possible values: 122 123 - 0 - Disable handshake limitation 124 - 1 - Enable handshake limitation 125 126 Default: 0 (disable) 127 128hs_ctrl - STRING 129 Select the SMC handshake control profile by name. 130 131 This string refers to the name of a user-implemented 132 BPF struct_ops instance of type smc_hs_ctrl. 133 134 The selected profile controls whether SMC options are advertised 135 during TCP SYN/SYN-ACK handshake. 136 137 Only available when CONFIG_SMC_HS_CTRL_BPF is enabled. 138 Write an empty string to clear the current profile. 139 140 Default: empty string 141