When SNC mode is enabled, create subdirectories and files to monitor
at the SNC node granularity. Legacy behavior is preserved by tagging
the monitor files at the L3 granularity with the "sum" attribute.
When the user reads these files the kernel will read monitor data
from all SNC nodes that share the same L3 cache instance and return
the aggregated value to the user.
Note that the "domid" field for files that must sum across SNC domains
has the L3 cache instance id, while non-summing files use the domain id.
The "sum" files do not need to make a call to mon_event_read() to
initialize the MBM counters. This will be handled by initializing the
individual SNC nodes that share the L3.
Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
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