ACC Utilities Reference Guide

TTGEN - ZCOM System Table Generator
Memory Image File Overview
Chapter 2 31
Buffer Pool
The buffer pool is a piece of fixed-size, contiguous memory. Its total size
is specified in the TTGEN configuration file. The system allocates
memory from this pool for ZCOM requests that require buffering (for
example, zsend), and returns memory to this pool on completion. The
memory allocated is always large enough to hold the whole request in
one contiguous memory block. The first four words of each allocated
buffer contains pointer and linkage information, the data area contains
the message header and message data. The message header contains
information that relates to the messages, such as the message type, the
destination and source nodes and ZLUs. The buffers are chained together
to form a First-In-First-Out queue. Queue headers are used to keep track
of and manipulate the buffers. For more detail, see the data structures
zbhd_type (buffer header) and zfbh_type (free buffer header) in
/opt/acc/include/zcom/zcomsys.h.