dat_srq_resize

- modify the size of the shared receive queue

Synopsis

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

DAT_RETURN
    dat_srq_resize (
    IN      DAT_SRQ_HANDLE      srq_handle,
    IN      DAT_COUNT           srq_max_recv_dto
    )

Parameters

srq_handle

A handle for an instance of the SRQ.

srq_max_recv_dto

The new maximum number of Recv DTOs that Shared Receive Queue must hold.

Description

The dat_srq_resize() function modifies the size of the queue of SRQ.

Resizing of Shared Receive Queue should not cause any incoming messages on any of the EPs that use the SRQ to be lost. If the number of outstanding Recv buffers on the SRQ is larger then the requested srq_max_recv_dto, the operation returns DAT_INVALID_STATE and do not change SRQ. This includes not just the buffers on the SRQ but all outstanding Receive buffers that had been posted to the SRQ and whose completions have not reaped yet. Thus, the outstanding buffers include the buffers on SRQ, the buffers posted to SRQ at are at SRQ associated EPs, and the buffers posted to SRQ for which completions have been generated but not yet reaped by Consumer from recv_evds of the EPs that use the SRQ.

If the requested srq_max_recv_dto is below the SRQ low watermark, the operation returns DAT_INVALID_STATE and does not change SRQ.

Return Values

DAT_SUCCESS

The operation was successful.

DAT_INVALID_HANDLE

The srq_handle argument is an invalid DAT handle.

DAT_INVALID_PARAMETER

The srq_max_recv_dto argument is invalid.

DAT_INSUFFICIENT_RESOURCES

The operation failed due to resource limitations.

DAT_INVALID_STATE

Invalid state. Either the number of entries on the SRQ exceeds the requested SRQ queue length or the requested SRQ queue length is smaller than the SRQ low watermark.

Usage

The dat_srq_resize() function is required not to lose any buffers. Thus, it cannot shrink below the outstanding number of Recv buffers on SRQ. There is no requirement to shrink the SRQ to return DAT_SUCCESS.

The quality of the implementation determines how closely to the Consumer-requested value the Provider shrinks the SRQ. For example, the Provider can shrink the SRQ to the Consumer-requested value and if the requested value is smaller than the outstanding buffers on SRQ, return DAT_INVALID_STATE; or the Provider can shrink to some value larger than that requested by the Consumer but below current SRQ size; or the Provider does not change the SRQ size and still returns DAT_SUCCESS.

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

dat_srq_create(3DAT), dat_srq_free(3DAT), dat_srq_post_recv(3DAT), dat_srq_query(3DAT), dat_srq_set_lw(3DAT), libdat(3LIB), attributes(5)