Hi, Since Andi added:
commit 2c95afc1e83d93fac3be6923465e1753c2c53b0a Author: Andi Kleen <[email protected]> Date: Thu Jun 9 06:14:38 2016 -0700 perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86 $ perf stat -e ref-cycles ls <not counted> .... fails systematically because the ref-cycles is now used by the watchdog and given this is a system-wide pinned event, it monopolizes the fixed counter 2 which is the only counter able to measure this event. So we either redirect ref-cycles towards 0x013c (cpu_clk_unhalted:xlck) or another event maybe from the msr PMU, such as msr/tsc/ or we revert Andi's patch. Each of these solutions has problems: - 0x013c is that is counts supposedly at a fixed frequency (used to be 100Mhz) but this is not guaranteed and user would still need to figure out ref frequency of CPU to compare with core cycles - msr/tsc/ counts in halted state. Recent paranoid default changes, make it not supported by default. msr/tsc/ counts user/kernel, with paranoid=2, it does not work - Revert Andi's patch, makes everything working again at the cost of multiplexing for topdown. It is not clear to me why topdown would be so sensitive to multiplexing compared to other metrics. Any comment? Thanks
