Setting up the channel measurement facility

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Red Hat Enterprise Linux 8.6 LPAR mode z/VM guest

Configure the channel measurement facility by adding parameters to the kernel parameter file.

Figure 1. Channel measurement facility kernel parameters

1! cmf.format=-1
1 cmf.format=
2.1 0
2.1 1
1! cmf.maxchannels=1024
1 cmf.maxchannels=<no_channels>(1)
Notes:
  • 1 If you specify both parameter=value pairs, separate them with a blank.
where:
cmf.format
defines the format, 0 for basic and 1 for extended, of the channel measurement blocks. The default, -1, uses the extended format.
cmf.maxchannels=<no_channels>
limits the number of devices for which data measurement can be enabled concurrently with the basic format. The maximum for <no_channels> is 4096. A warning is printed if more than 4096 channels are specified. The channel measurement facility might still work; however, specifying more than 4096 channels causes a high memory consumption.

For the extended format, there is no limit and any value you specify is ignored.