Interface Attributes (Detailed Kernel Trace)

The detailed kernel trace provides easy access to the AXI transactions and their properties. The AXI transactions are presented for the DDR side (Memory Data Transfers) as well as the Kernel side (Kernel "pass" 1:1:1) of the AXI interconnect. The following figure illustrates a typical kernel trace of a newly accelerated algorithm.

Most interesting with respect to performance are the fields:
  • Burst Length: Which describes how many packages are sent within one transaction
  • Burst Size: Which describes the number of bytes being transferred as part of one package

Given a Burst Length of 1 and just 4 Bytes per package, it will require many individual AXI transactions to transfer any reasonable amount of data. It should be noted, that SDx™ never creates burst sizes less than 4 bytes even if smaller data is transmitted. In this case, if consecutive items are accessed without AXI bursts enabled, it is possible to observe multiple AXI reads to the same address.

Small Burst Lengths as well as Burst Sizes considerably less than 512 Bits are therefore good opportunities to optimize interface performance. The following sections show improved implementations:
  • Using Burst Data Transfers
  • Utilize Full User Data Width of Memory Bandwidth