After I installed papi 4.1.0, I ran make test, which gave me the error: PAPI Error: vperfctr_open() returned NULL, please run perfex -i to verify your perfctr installation.
perfex -i gave me: perfex: open perfctrs: No such file or directory.
I didn't patch the kernel, since INSTALL.txt says it is not necessary for kernel later than 2.6.31. However, /dev/perfctr does not exist in my system. Does that mean I should patch the kernel anyway?