Specifying the number of inbound buffers

Red Hat Enterprise Linux 9.2 LPAR mode z/VM guest

Depending on the amount of available storage and the amount of traffic, you can assign 8 - 128 inbound buffers for each qeth group device.

Before you begin

The device must be offline while you specify the number of inbound buffers.

About this task

By default, the qeth device driver assigns 64 inbound buffers to OSA devices and 128 to HiperSockets™ devices.

The Linux® memory usage for inbound data buffers for the devices is (number of buffers) × (buffer size).

The buffer size is equivalent to the frame size, which depends on the type of CHPID:

For an OSA-Express CHPID in QDIO mode: 64 KB
For HiperSockets: depending on the HiperSockets CHPID definition, 16 KB, 24 KB, 40 KB, or 64 KB

Procedure

Set the buffer_count attribute to the number of inbound buffers you want to assign.

Issue a command of the form:

# chzdev <device_type> <device_bus_id> buffer_count=<number>

or, using sysfs:

# echo <number> > /sys/bus/ccwgroup/drivers/qeth/<device_bus_id>/buffer_count

Example

In this example, an operational device 0.0.a000 is first set offline, 64 inbound buffers are assigned to the device, and then the device is set back online:

# chzdev -d -a 0.0.a000 
# chzdev 0.0.a000 buffer_count=64 
# chzdev -e -a 0.0.a000

or, using sysfs:

# echo 0 > /sys/bus/ccwgroup/drivers/qeth/0.0.a000/online
# echo 64 > /sys/bus/ccwgroup/drivers/qeth/0.0.a000/buffer_count
# echo 1 > /sys/bus/ccwgroup/drivers/qeth/0.0.a000/online