Tribblix: manual page: dat_ep_post_rdma

DAT_EP_POST_RDMA_READ(3DAT) Direct Access Transport Library Functions

NAME

dat_ep_post_rdma_read - transfer all data to the local data buffer

SYNOPSIS

cc [ flag... ] file... -ldat [ library... ]
#include <dat/udat.h>

DAT_RETURN
dat_ep_post_rdma_read (
IN DAT_EP_HANDLE ep_handle,
IN DAT_COUNT num_segments,
IN DAT_LMR_TRIPLET *local_iov,
IN DAT_DTO_COOKIE user_cookie,
IN DAT_RMR_TRIPLET *remote_buffer,
IN DAT_COMPLETION_FLAGS completion_flags
)

PARAMETERS

ep_handle
Handle for an instance of the Endpoint.

num_segments
Number of lmr_triplets in local_iov.

local_iov
I/O Vector that specifies the local buffer to
fill.

user_cookie
User-provided cookie that is returned to the
Consumer at the completion of the RDMA Read. Can
be NULL.

remote_buffer
A pointer to an RMR Triplet that specifies the
remote buffer from which the data is read.

completion_flags
Flags for posted RDMA Read. The default
DAT_COMPLETION_DEFAULT_FLAG is 0x00. Other values
are as follows:

Completion Suppression
DAT_COMPLETION_SUPPRESS_FLAG

0x01
Suppress
successful
Completion.

Notification of Completion
DAT_COMPLETION_UNSIGNALLED_FLAG

0x04
Non-
notification
completion.
Local
Endpoint
must be
configured
for
Notification
Suppression.

Barrier Fence
DAT_COMPLETION_BARRIER_FENCE_FLAG

0x08
Request for
Barrier
Fence.

DESCRIPTION

The dat_ep_post_rdma_read() function requests the transfer of all the
data specified by the remote_buffer over the connection of the
ep_handle Endpoint into the local_iov.

The num_segments parameter specifies the number of segments in the
local_iov. The local_iov segments are filled in the I/O Vector order
until the whole message is received. This ensures that all the
"front" segments of the local_iov I/O Vector are completely filled,
only one segment is partially filled, if needed, and all segments
that follow it are not filled at all.

The user_cookie allows Consumers to have unique identifiers for each
DTO. These identifiers are completely under user control and are
opaque to the Provider. There is no requirement on the Consumer that
the value user_cookie should be unique for each DTO. The user_cookie
is returned to the Consumer in the Completion event for the posted
RDMA Read.

A Consumer must not modify the local_iov or its content until the DTO
is completed. When a Consumer does not adhere to this rule, the
behavior of the Provider and the underlying Transport is not defined.
Providers that allow Consumers to get ownership of the local_iov but
not the memory it specifies back after the dat_ep_post_rdma_read()
returns should document this behavior and also specify its support in
Provider attributes. This behavior allows Consumers full control of
the local_iov after dat_ep_post_rdma_read() returns. Because this
behavior is not guaranteed by all Providers, portable Consumers
should not rely on this behavior. Consumers should not rely on the
Provider copying local_iov information.

The completion of the posted RDMA Read is reported to the Consumer
asynchronously through a DTO Completion event based on the specified
completion_flags value. The value of DAT_COMPLETION_UNSIGNALLED_FLAG
is only valid if the Endpoint Request Completion Flags
DAT_COMPLETION_UNSIGNALLED_FLAG. Otherwise, DAT_INVALID_PARAMETER is
returned.

The DAT_SUCCESS return of the dat_ep_post_rdma_read() is at least the
equivalent of posting an RDMA Read operation directly by native
Transport. Providers should avoid resource allocation as part of
dat_ep_post_rdma_read() to ensure that this operation is nonblocking
and thread safe for an UpCall.

The operation is valid for the Endpoint in the DAT_EP_STATE_CONNECTED
and DAT_EP_STATE_DISCONNECTED states. If the operation returns
successfully for the Endpoint in the DAT_EP_STATE_DISCONNECTED state,
the posted RDMA Read is immediately flushed to request_evd_handle.

RETURN VALUES

DAT_SUCCESS
The operation was successful.

DAT_INSUFFICIENT_RESOURCES
The operation failed due to resource
limitations.

DAT_INVALID_PARAMETER
Invalid parameter. For example, one of
the IOV segments pointed to a memory
outside its LMR.

DAT_INVALID_HANDLE
The ep_handle parameter is invalid.

DAT_INVALID_STATE
A parameter is in an invalid state.
Endpoint was not in the
DAT_EP_STATE_CONNECTED or
DAT_EP_STATE_DISCONNECTED state.

DAT_LENGTH_ERROR
The size of the receiving buffer is too
small for sending buffer data. The size
of the local buffer is too small for
the data of the remote buffer.

DAT_PROTECTION_VIOLATION
Protection violation for local or
remote memory access. Protection Zone
mismatch between either an LMR of one
of the local_iov segments and the local
Endpoint or the rmr_context and the
remote Endpoint.

DAT_PRIVILEGES_VIOLATION
Privileges violation for local or
remote memory access. Either one of the
LMRs used in local_iov is invalid or
does not have the local write
privileges, or rmr_context does not
have the remote read privileges.

USAGE

For best RDMA Read operation performance, the Consumer should align
each buffer segment of local_iov to the Optimal Buffer Alignment
attribute of the Provider. For portable applications, the Consumer
should align each buffer segment of local_iov to the
DAT_OPTIMAL_ALIGNMENT.

If connection was established without outstanding RDMA Read
attributes matching on Endpoints on both sides (outstanding RDMA Read
outgoing on one end is larger than the outstanding RDMA Read incoming
on the other end), connection is broken when the number of incoming
RDMA Read exceeds the outstanding RDMA Read incoming attribute of the
Endpoint. The Consumer can use its own flow control to ensure that it
does not post more RDMA Reads then the remote EP outstanding RDMA
Read incoming attribute is. Thus, they do not rely on the underlying
Transport enforcing it.

ATTRIBUTES