On 23/09/2021 08:46, Ian Rogers wrote:

For a metric like:
   EVENT1 if #smt_on else EVENT2
     
currently EVENT1 and EVENT2 will be measured and then when the metric
is reported EVENT1 or EVENT2 will be printed depending on the value
from smt_on() during the expr parsing. Computing both events is
unnecessary and can lead to multiplexing as discussed in this thread:
https://lore.kernel.org/lkml/20201110100346.2527031-1-irogers@google.com/ (local)

This change modifies expression parsing so that constants are
considered when building the set of ids (events) and only events not
contributing to a constant value are measured.

Based on some testing on my arm64 platform, no regression seen, so:

Tested-by: John Garry <redacted>