X25AM Configuration and Management Manual

Configuring an X25AM Subsystem
X25AM Configuration and Management Manual—523424-004
3-21
Numeric Range Validation
The default value of 50 pages should be sufficient for most customer configurations.
However, for large server configurations, you should calculate the total amount of
memory needed for all level-3 holding buffers to ensure that enough
EXTENDEDPOOLPAGES are reserved. If there are not enough pool pages reserved,
file-system error 33 (I/O process is unable to obtain buffer space) is returned.
The total amount of memory needed for a single circuit (N) is the sum of OCB^SIZE,
HOLDING^BUFFER^SIZE, and FILE^SYSTEM REQUEST^BUFFER^SIZE.
Calculations (in bytes) for each of these variables and for the total value (in pages) of
EXTENDEDPOOLPAGES are as follows:
HOLDING^BUFFER^SIZE =
(packet size + 7 ) * ( L3window size) + 48
= 318 (packet size 128, window 2)
= 1889 (packet size 256, window 7)
For PTP or ITI subdevices,
or READ or WRITE BUFFER^SIZE = MAXIOSIZE
Note: MAXIOSIZE defaults to 4096 bytes
For NAM subdevices, BUFFER SIZE =
(Expand packet size + 12) * [min (expand window size,7) + 1]
For QLLC subdevices, BUFFER SIZE =
(SNAX packet size + 16) * [min [(SNAX window size * 2 + 1), 7] + 1]
Size^Of^Bytes
for a single circuit = HOLDING^BUFFER^SIZE
+ BUFFER SIZE
EXTENDEDPOOLPAGES =
[sum of Size^Of^Bytes for each circuit]/ 2048
(This value should be rounded up.)
Example:
This example of estimating EXTENDEDPOOLPAGES uses the values of 50 circuits
configured, 128-byte packet size, L3 window of 7 with five opens, and default
MAXIOSIZE. Two methods of calculation are provided. The first method provides a
conservative estimate, ensuring a configuration that is less likely to run out of memory.
HOLDING^BUFFER^SIZE = (128 + 7) * 7 + 48 = 993
FILE^SYSTEM^REQUEST^BUFFER^SIZE = 4096 + 6 = 4102
TOTAL BYTES PER CIRCUIT = 993 + 4102 = 5095
TOTAL PAGES PER CIRCUIT = 5095 / 2048 = 3 (rounded up)
50 circuits * 3 = 150
NUMBER OF EXTENDEDPOOLPAGES = 150 + 10 = 160 (conservative)
If you would like to reserve seven pages, you could use the following less-conservative
method of calculating extended pages:
(NUMBER OF CIRCUITS * TOTAL BYTES PER CIRCUIT) / 2048 =
NUMBER OF EXTENDEDPOOLPAGES
Note. You need to add 10 pages to the calculated number of EXTENDEDPOOLPAGES to
accommodate memory fragmentation and the SPI reply buffer, which may require up to 5 KB.