From fb4907f487254375830f135dcfe5dd7e6f8b705f Mon Sep 17 00:00:00 2001 From: Chao Leng Date: Fri, 25 Nov 2022 09:00:26 +0800 Subject: RDMA/cma: Change RoCE packet life time from 18 to 16 The ack timeout retransmission time is affected by the following two factors: one is packet life time, another is the HCA processing time. Now the default packet lifetime(CMA_IBOE_PACKET_LIFETIME) is 18. That means the minimum ack timeout is 2 seconds (2^(18+1)*4us=2.097seconds). The packet lifetime means the maximum transmission time of packets on the network, 2 seconds is too long. Assume the network is a clos topology with three layers, every packet will pass through five hops of switches. Assume the buffer of every switch is 128MB and the port transmission rate is 25 Gbit/s, the maximum transmission time of the packet is 200ms(128MB*5/25Gbit/s). Add double redundancy, it is less than 500ms. So change the CMA_IBOE_PACKET_LIFETIME to 16, the maximum transmission time of the packet will be about 500+ms, it is long enough. Link: https://lore.kernel.org/r/20221125010026.755-1-lengchao@huawei.com Signed-off-by: Chao Leng Signed-off-by: Jason Gunthorpe --- drivers/infiniband/core/cma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/infiniband/core/cma.c') diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c index cc2222b85c88..2f5b5e6f3d11 100644 --- a/drivers/infiniband/core/cma.c +++ b/drivers/infiniband/core/cma.c @@ -47,7 +47,7 @@ MODULE_LICENSE("Dual BSD/GPL"); #define CMA_CM_RESPONSE_TIMEOUT 20 #define CMA_MAX_CM_RETRIES 15 #define CMA_CM_MRA_SETTING (IB_CM_MRA_FLAG_DELAY | 24) -#define CMA_IBOE_PACKET_LIFETIME 18 +#define CMA_IBOE_PACKET_LIFETIME 16 #define CMA_PREFERRED_ROCE_GID_TYPE IB_GID_TYPE_ROCE_UDP_ENCAP static const char * const cma_events[] = { -- cgit