Ignore unnecessary I/O devices
A Linux® LPAR should contain only those I/O devices that it uses.
A mainframe environment often includes numerous I/O devices. Especially for Linux in LPAR mode, more of these I/O devices might be available to a
particular instance of Linux on IBM® Z than needed. Limit the I/O
devices by:
- Adding only the needed devices to the applicable LPAR in the IOCDS.
z/VM and KVM: Making only needed devices available to guests.
- Using the cio_ignore= kernel parameter to ignore all devices that are not currently in use by
this instance of Linux on IBM Z.
If more devices are needed later, they can be dynamically removed from the list of devices to be ignored. Use the cio_ignore kernel parameter or the /proc/cio_ignore dynamic control to remove devices.
Rationale: Numerous unused devices can cause:
- Unnecessary high memory usage due to allocation of device structures.
- Unnecessary high load on status changes because hot-plug handling must be done for every device found.
- Prolonged boot and shutdown time.