Using z/VM VSWITCH

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In this test case, the network interface for interconnecting the z/VM® guest systems was changed from a HiperSockets configured guest LAN to a VSWITCH configured LAN.

The following z/VM commands were used to set up the two VSWITCH network interfaces.

DEF VSWITCH testsw1 RDEV none CONNECT VLAN 1 PORTTYPE ACCESS CONTROLLER DTCVSW1
PRIROUTER PORTNAME PORT30

SET VSWITCH testsw1 GRANT DTCVSW1 vlan 1
SET VSWITCH testsw1 GRANT LNX00085 vlan 1
SET VSWITCH testsw1 GRANT LNX00090 vlan 1
SET VSWITCH testsw1 GRANT LNX00091 vlan 1
DEF VSWITCH testsw2 RDEV none CONNECT VLAN 2 PORTTYPE ACCESS CONTROLLER DTCVSW1
PRIROUTER PORTNAME PORT30

SET VSWITCH testsw2 GRANT DTCVSW1 vlan 2
SET VSWITCH testsw2 GRANT LNX00080 vlan 2
SET VSWITCH testsw2 GRANT LNX00081 vlan 2
SET VSWITCH testsw2 GRANT LNX00082 vlan 2
SET VSWITCH testsw2 GRANT LNX00083 vlan 2
SET VSWITCH testsw2 GRANT LNX00084 vlan 2
SET VSWITCH testsw2 GRANT LNX00086 vlan 2
SET VSWITCH testsw2 GRANT LNX00090 vlan 2

To connect a guest to the VSWITCH, run the following two CP commands to define a nic and then couple the nic to the VSWITCH.

For VSWITCH testsw1:


DEFINE NIC 6200 QDIO
COUPLE 6200 TO SYSTEM testsw1

For VSWITCH testsw2:

DEFINE NIC 6203 QDIO
COUPLE 6203 TO SYSTEM testsw2

The environment with the WebSphere® proxy server was used for this test.

All runs were done with the cache configuration described in Table 1.

Table 1. Cache definitions - Using z/VM VSWITCH
DynaCache size	Caching mode	Servlet caching	Replication domain	Replication type
20000	Distributed map	Disabled	Entire domain	Not shared

Figure 1 illustrates the throughput when using a guest LAN versus a VSWITCH LAN. Figure 2 illustrates the response time when using a guest LAN versus a VSWITCH LAN.

This figure shows the throughput comparison of the guest LAN versus VSWITCH LAN — Figure 1. Throughput Comparison - guest LAN versus VSWITCH LAN.

This figure shows the response time comparison, guest LAN versus VSWITCH LAN. — Figure 2. Response Time Comparison - guest LAN versus VSWITCH LAN.

Figure 3 illustrates the CPU utilization when using a guest LAN versus a VSWITCH LAN.

This figure shows the CPU comparison, guest LAN versus VSWITCH LAN — Figure 3. CPU comparison - guest LAN versus VSWITCH LAN

Observations

Configuring a z/VM VSWITCH LAN produced an improvement of approximately 8% in throughput and an increase in response time. Total CPU utilization for the VSWITCH case is higher than the guest LAN case.

Figure 4 shows where the additional CPU utilization is spent. There is significant increase in WebSphere CPU utilization. The total CPU used increased up to 10%, which indicates in relation to the 8% throughput improvement, a slight increase in CPU cost per transaction.

This figure shows the relative CPU increase for VSWITCH versus a guest LAN per server type. — Figure 4. CPU utilization comparison - VSWITCH versus guest LAN

Note: The values were stacked to show the increase of the utilization in total.

Conclusion

Whenever possible, the z/VM VSWITCH function should be used instead of the z/VM guest LAN function.