Internal shared memory device driver

Red Hat Enterprise Linux 9.2 LPAR mode z/VM guest

The internal shared memory (ISM) device driver provides virtual PCI devices for shared memory communications direct (SMC-D).

Red Hat® Enterprise Linux® loads the ISM module when a device is activated. The module has no parameters.

ISM devices are defined in the IOCDS. Each ISM definition includes a physical network ID (PNET ID) to associate the ISM device with Ethernet devices.

The following figure illustrates how an ISM device and a HiperSockets device are associated by a matching PNET ID. A communication peer on the same CPC has a similarly associated pair of an ISM device and HiperSockets device. With this setup, the TCP connection can switch over to an SMC-D connection over the SMC protocol.
Figure 1. A matching PNET ID associates ISM devices and Ethernet devices
This graphic is described in the preceding text.

For information about how to find the PNET ID of PCI devices from your Linux instance, see Investigating PNET IDs.

Use the smcd command to explore SMC-D link groups and devices, see smcd - Display information about SMC-D link groups and devices.