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Diffstat (limited to 'Documentation/networking/smc-sysctl.rst')
| -rw-r--r-- | Documentation/networking/smc-sysctl.rst | 60 |
1 files changed, 56 insertions, 4 deletions
diff --git a/Documentation/networking/smc-sysctl.rst b/Documentation/networking/smc-sysctl.rst index 6d8acdbe9be1..904a910f198e 100644 --- a/Documentation/networking/smc-sysctl.rst +++ b/Documentation/networking/smc-sysctl.rst @@ -44,18 +44,70 @@ smcr_testlink_time - INTEGER 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 + Default: 64KiB 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 + 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 + +smcr_max_send_wr - INTEGER + So-called work request buffers are SMCR link (and RDMA queue pair) level + resources necessary for performing RDMA operations. Since up to 255 + connections can share a link group and thus also a link and the number + of the work request buffers is decided when the link is allocated, + depending on the workload it can be a bottleneck in a sense that threads + have to wait for work request buffers to become available. Before the + introduction of this control the maximal number of work request buffers + available on the send path used to be hard coded to 16. With this control + it becomes configurable. The acceptable range is between 2 and 2048. + + Please be aware that all the buffers need to be allocated as a physically + continuous array in which each element is a single buffer and has the size + of SMC_WR_BUF_SIZE (48) bytes. If the allocation fails, we keep retrying + with half of the buffer count until it is ether successful or (unlikely) + we dip below the old hard coded value which is 16 where we give up much + like before having this control. + + Default: 16 + +smcr_max_recv_wr - INTEGER + So-called work request buffers are SMCR link (and RDMA queue pair) level + resources necessary for performing RDMA operations. Since up to 255 + connections can share a link group and thus also a link and the number + of the work request buffers is decided when the link is allocated, + depending on the workload it can be a bottleneck in a sense that threads + have to wait for work request buffers to become available. Before the + introduction of this control the maximal number of work request buffers + available on the receive path used to be hard coded to 16. With this control + it becomes configurable. The acceptable range is between 2 and 2048. + + Please be aware that all the buffers need to be allocated as a physically + continuous array in which each element is a single buffer and has the size + of SMC_WR_BUF_SIZE (48) bytes. If the allocation fails, we keep retrying + with half of the buffer count until it is ether successful or (unlikely) + we dip below the old hard coded value which is 16 where we give up much + like before having this control. + + Default: 48 |