DAT_LMR_SYNC_RDMA_READ(3DAT)DAT_LMR_SYNC_RDMA_READ(3DAT)NAMEdat_lmr_sync_rdma_read - synchronize local memory with RDMA read on
non-coherent memory
SYNOPSIS
cc [ flag... ] file... -ldat [ library... ]
#include <dat/udat.h>
DAT_RETURN
dat_lmr_sync_rdma_read (
IN DAT_IA_HANDLE ia_handle,
IN const DAT_LMR_TRIPLET *local_segments,
IN DAT_VLEN num_segments
)
PARAMETERS
ia_handle
A handle for an open instance of the IA.
local_segments
An array of buffer segments.
num_segments
The number of segments in the local_segments argu‐
ment.
DESCRIPTION
The dat_lmr_sync_rdma_read() function makes memory changes visible to
an incoming RDMA Read operation. This operation guarantees consistency
by locally flushing the non-coherent cache prior to it being retrieved
by remote peer RDMA read operations.
The dat_lmr_sync_rdma_read() function is needed if and only if the
Provider attribute specifies that this operation is needed prior to an
incoming RDMA Read operation. The Consumer must call
dat_lmr_sync_rdma_read() after modifying data in a memory range in this
region that will be the target of an incoming RDMA Read operation. The
dat_lmr_sync_rdma_read() function must be called after the Consumer has
modified the memory range but before the RDMA Read operation begins.
The memory range that will be accessed by the RDMA read operation must
be supplied by the caller in the local_segments array. After this call
returns, the RDMA Read operation can safely see the modified contents
of the memory range. It is permissible to batch synchronizations for
multiple RDMA Read operations in a single call by passing a local_seg‐
ments array that includes all modified memory ranges. The local_seg‐
ments entries need not contain the same LMR and need not be in the same
Protection Zone.
If the Provider attribute specifying that this operation is required
attempts to read from a memory range that is not properly synchronized
using dat_lmr_sync_rdma_read(), the returned contents are undefined.
RETURN VALUES
DAT_SUCCESS
The operation was successful.
DAT_INVALID_HANDLE
The DAT handle is invalid.
DAT_INVALID_PARAMETER
One of the parameters is invalid. For example,
the address range for a local segment fell
outside the boundaries of the corresponding
Local Memory Region or the LMR handle was
invalid.
USAGE
Determining when an RDMA Read will start and what memory range it will
read is the Consumer's responsibility. One possibility is to have the
Consumer that is modifying memory call dat_lmr_sync_rdma_read() and
then post a Send DTO message that identifies the range in the body of
the Send. The Consumer wanting to perform the RDMA Read can receive
this message and know when it is safe to initiate the RDMA Read opera‐
tion.
This call ensures that the Provider receives a coherent view of the
buffer contents upon a subsequent remote RDMA Read operation. After the
call completes, the Consumer can be assured that all platform-specific
buffer and cache updates have been performed, and that the LMR range
has consistency with the Provider hardware. Any subsequent write by the
Consumer can void this consistency. The Provider is not required to
detect such access.
The action performed on the cache before the RDMA Read depends on the
cache type:
o I/O noncoherent cache will be invalidated.
o CPU noncoherent cache will be flushed.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌────────────────────┬──────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼──────────────────────┤
│Interface Stability │ Standard: uDAPL, 1.2 │
├────────────────────┼──────────────────────┤
│MT-Level │ Unsafe │
└────────────────────┴──────────────────────┘
SEE ALSOdat_lmr_sync_rdma_write(3DAT), libdat(3LIB), attributes(5)
Jul 16, 2004 DAT_LMR_SYNC_RDMA_READ(3DAT)
