6.3 Buffer Usage Tips

The following guidelines apply to both SpringWare boards and DM3 boards:

• The smaller you make the driver buffer size or transfer buffer size, the more interrupts are generated to handle the buffers, and consequently, there is an associated increase in CPU loading. Therefore, you must choose this value carefully to maximize throughput while minimizing system load.
• The speed of the host processor, as well as other concurrent processing, has an impact on how low the buffers can be set.

For SpringWare boards only. When adjusting buffer sizes on SpringWare boards, keep the following guidelines in mind:

• In general, the driver buffer size should be at least two times the size of the firmware buffer. For ASR applications, the driver buffer size should be at least three times the size of the firmware buffer. If it isn't, play/record may terminate abruptly and data loss may occur.

  For example, if the firmware buffer size is 512 bytes, then the driver buffer size in ASR applications should be at least 1536 bytes. See Table6-1, Types of Buffers Used in CSP (SpringWare Boards) for driver buffer size limitations in Linux.

• Simply reducing the driver buffer size does not guarantee better performance. In fact, if the value is poorly chosen, the exact opposite may result.

For DM3 boards only. When adjusting buffer sizes on DM3 boards, keep the following guideline in mind:

• For ASR applications, set the transfer buffer size to a value less than or equal to 2 kbytes so that no host buffering is performed, for minimal latency.

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