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IB/cma: Introduce rdma_set_min_rnr_timer()

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Introduce the ability for kernel ULPs to adjust the minimum RNR Retry
timer. The INIT -> RTR transition executed by RDMA CM will be used for
this adjustment. This avoids an additional ib_modify_qp() call.

rdma_set_min_rnr_timer() must be called before the call to rdma_connect()
on the active side and before the call to rdma_accept() on the passive
side.

The default value of RNR Retry timer is zero, which translates to 655
ms. When the receiver is not ready to accept a send messages, it encodes
the RNR Retry timer value in the NAK. The requestor will then wait at
least the specified time value before retrying the send.

The 5-bit value to be supplied to the rdma_set_min_rnr_timer() is
documented in IBTA Table 45: "Encoding for RNR NAK Timer Field".

Link: https://lore.kernel.org/r/1617216194-12890-2-git-send-email-haakon.bugge@oracle.com
Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Acked-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
This commit is contained in:
Håkon Bugge
2021-03-31 20:43:13 +02:00
committed by Jason Gunthorpe
parent 8166e00905
commit 3aeffc46af
3 changed files with 45 additions and 0 deletions
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2
include/rdma/rdma_cm.h
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@@ -331,6 +331,8 @@ int rdma_set_reuseaddr(struct rdma_cm_id *id, int reuse);
int rdma_set_afonly(struct rdma_cm_id *id, int afonly);
int rdma_set_ack_timeout(struct rdma_cm_id *id, u8 timeout);
int rdma_set_min_rnr_timer(struct rdma_cm_id *id, u8 min_rnr_timer);
/**
* rdma_get_service_id - Return the IB service ID for a specified address.
* @id: Communication identifier associated with the address.