Chapter 2
NI 5450 Overview
NI PXIe-5450 User Manual
2-70
ni.com
Improving Streaming Performance
To improve your maximum sustainable transfer rate for streaming,
consider the following recommendations:
•
Adjust the Data Transfer Block Size property or the
NIFGEN_ATTR_DATA_TRANSFER_BLOCK_SIZE
attribute. The default
data transfer block size for NI-FGEN is 2 MS (or 4 MB). If you were
to write a 16 MB waveform to the signal generator, the complete
transfer would occur using four separate DMA transfers. If you modify
the data transfer block size to 8 MS (16 MB), for example, the data
transfer is more efficient and is instead accomplished in a single
transfer.
•
Configure advanced streaming properties by calling the Maximum
In-Flight Read Requests, PCI DMA Optimization Enabled, or
Preferred Packet Size property or the
NIFGEN_ATTR_DATA_TRANSFER_MAXIMUM_IN_FLIGHT_READS
,
NIFGEN_ATTR_DATA_TRANSFER_PCI_DMA_OPTIMIZATIONS
, or
NIFGEN_ATTR_DATA_TRANSFER_PREFERRED_PACKET_SIZE
attributes.
•
Optimize the bus bandwidth usage for multi-device streaming
applications by calling the Maximum Bandwidth property or the
NIFGEN_ATTR_DATA_TRANSFER_MAXIMUM_BANDWIDTH
attribute.
•
When streaming from hard drives, consider the hard drive speed for
maximum sustainable rates. Laptop hard drives typically have a data
transfer rate of 25 to 30 MB/s. Desktop hard drives often can meet
55 to 70 MB/s.
Transfer rates from hard drives can vary for a number of reasons, including
where the data is physically stored on the hard drive and how much data is
stored. Storing your waveform files on a fairly empty, defragmented hard
drive may help increase performance.
•
Consider using a redundant array of independent disks (RAID)
configuration to utilize striping to increase data transfer rates from
disk.
•
When using 18-slot PXI chassis, install the signal generator used for
streaming in the first segment (Slots 2 to 6) of the PXI chassis.
•
Utilize Direct DMA.
