ACC Utilities Reference Guide

Chapter 2 39
TTGEN - ZCOM System Table Generator
Creating the TTGEN Configuration File
Buffer-Pool
Block of memory (freebufferarea), from which all buffers are allocated to
the ZCOM sub-system. The range of valid values is 1024…2147483645
(0x7FFFFFF, ZCOM_MAXBPOOL in
/opt/acc/include/zcom/zcomsys.h). Default is 3 Mbytes. M ust be a
multiple of 4. The kernel memory plus the ZCOM memory size cannot
exceed available physical memory. The recommended minimum is 200
Kbyte (e.g., for a small test environment). The buffer pool plus the size o f
the ZCOM tables should not exceed the amount of memory gen’d into the
kernel for the ZCOM subsystem (controlled through the zcom_mem_size
parameter in the system file). For a production environment, use the
following method to estimate the required Buffer-Pool size:
BUFFER-POOL size = <Card> x <Rate> x <Time> x (<Length> + 200) x 1.5
<Card> number of ACC cards in system
<Rate> maximum number of messages per second per ACC
card
<Time> average turn-around time, in seconds, for one message
(including transmission time). This also depends on
SPU processing power. For most systems, 5 seconds
should be adequate.
<Length> average message length
200 is the memory overhead per message (in bytes).
1.5 is the scaling factor to allow for usable gaps in buffer pool
Example:
For a 100% busy system with 8 mux cards with 57.6k links, and an
average message length of 100 bytes, the Buffer-Pool size should be at
least:
8x576x5x(100+200) x 1.5 = 10 Mbytes