Whats multiplexing?
Many systems have only a few hardware performance counter registers; thus you can only measure a few metrics at once. Some platforms may support counter multiplexing, which gives the user the illusion of a larger number of registers by time sharing the performance registers. On the MIPS R10K series, the IRIX kernel supports multiplexing, allowing up to 32 events to be counted at once. On other platforms PAPI does the multiplexing itself, swapping events in and out of the counters based on a timer interrupt. Don’t take fine grained measurements when multiplexing, unless you know what you’re doing.
Related Questions
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