diff --git a/srpt/README b/srpt/README index b4e4cd0ba..2acf741cf 100644 --- a/srpt/README +++ b/srpt/README @@ -62,27 +62,31 @@ Proceed as follows to compile and install the SRP target driver: chkconfig scst on The ib_srpt kernel module supports the following parameters: -* srp_max_message_size (number) +* srp_max_req_size (number) Maximum size of an SRP control message in bytes. Examples of SRP control messages are: login request, logout request, data transfer request, ... The larger this parameter, the more scatter/gather list elements can be sent at once. Use the following formula to compute an appropriate value for this parameter: 68 + 16 * (sg_tablesize). The default value of this parameter is 2116, which corresponds to an sg table size of 128. +* srp_max_rsp_size (number) + Maximum size of an SRP response message in bytes. Sense data is sent back + via these messages towards the initiator. The default size is 256 bytes. + With this value there remains (256-36) = 220 bytes for sense data. * srp_max_rdma_size (number) Maximum number of bytes that may be transferred at once via RDMA. Defaults to 65536 bytes, which is sufficient to use the full bandwidth of low-latency HCAs. Increasing this value may decrease latency for applications transferring large amounts of data at once. -* srpt_autodetect_cred_req (y or n, default n) - Whether or not to autodetect initiator support for SRP_CRED_REQ (initiators - with Linux kernel 2.6.37 or later only). The use of SRP_CRED_REQ allows - ib_srpt to process workloads with large I/O depths more efficiently. - Note: enabling this mode causes the Windows SRP initiator to stop working. * srpt_srq_size (number, default 4095) ib_srpt uses a shared receive queue (SRQ) for processing incoming SRP requests. This number may have to be increased when a large number of initiator systems is accessing a single SRP target system. +* srpt_sq_size (number, default 4096) + Per-channel InfiniBand send queue size. The default setting is sufficient + for a credit limit of 128. Changing this parameter to a smaller value may + cause RDMA requests to be retried and hence may slow down data transfer + severely. * thread (0, 1 or 2, default 1) Defines the context on which SRP requests are processed: * thread=0: do as much processing in IRQ context as possible. Results in @@ -194,7 +198,7 @@ Performance Notes - Initiator Side * For latency sensitive applications, using the noop scheduler at the initiator side can give significantly better results than with other schedulers. -* The following parameters have a small but measureable impact on SRP +* The following parameters have a small but measurable impact on SRP performance: * /sys/class/block/${dev}/queue/rotational * /sys/class/block/${dev}/queue/rq_affinity