On Wed, Nov 18, 2020 at 08:41:42AM +0100, Alexandre Chartre wrote: > Well, it looks like I wrongfully assume that KPTI was a well known performance > overhead since it was introduced (because it adds extra page-table switches), > but you are right I should be presenting my own numbers.
Here's one recipe, courtesy of Mel: https://github.com/gormanm/mmtests " ./run-mmtests.sh --no-monitor --config configs/config-workload-poundsyscall test-default # reboot the machine with pti disabled ./run-mmtests.sh --no-monitor --config configs/config-workload-poundsyscall test-nopti poundsyscall just calls getppid() so it's a light-weight syscall and a proxy measure for syscall entry/exit costs. To do the actual compare cd work/log ../../compare-kernels.sh and see what gain there is from disabling pti. If you want to compare the other direction ../../compare-kernels.sh --baseline test-nopti --compare test-default If you get an error about BinarySearch (echo y;echo o conf prerequisites_policy follow;echo o conf commit)|cpan yes | cpan List::BinarySearch Only se the second line if you want to interactively confirm what cpan should download and install." I've CCed him should you have any questions. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
