Setting the maximum buffer size
Use the buffer attribute to set the maximum buffer size of an IUCV device.
About this task
The upper limit for the maximum buffer size is 32768 bytes (32 KB). The lower limit is 580 bytes in general and in addition, if the interface is up and running <current MTU + header size>. The header space is typically 4 bytes.
Changing the buffer size is accompanied by an MTU size change to the value <buffer size - header size>.
To set the maximum buffer size, issue a command of this form:
# echo <value> > /sys/bus/iucv/drivers/netiucv/netiucv<n>/buffer
where:
- <value>
- is the number of bytes you want to set. If you specify a value outside the valid range, the command is ignored.
- <n>
- is an index that identifies the IUCV device and the corresponding interface.
Note: If IUCV performance deteriorates and IUCV issues out-of-memory messages on the console, consider using a buffer size less than
4K.
Example
In this example, the maximum buffer size of an IUCV device netiucv0 is set to 16384 byte.
# echo 16384 > /sys/bus/iucv/drivers/netiucv/netiucv0/buffer