On Wed, 29 Mar 2017 09:14:32 -0400 Rik van Riel <riel@xxxxxxxxxx> wrote: > > I failed to reproduce with your config. I'm still getting 99% > > userspace > > cputime. So I'm wondering if the hogging style plays a role. > > > > I run pure user loops: > > > > int main(int argc, char **argv) > > { > > for (;;); > > return 0 > > } > > > > Does your user program perform syscalls or IOs of some sort? > > Luiz's program makes a syscall every millisecond, > if started with the arguments he gave as his > reproducer. There are various reproducers actually. I started off with the simple loop above, then wrote the attach program and then wrote the one you're mentioning: http://people.redhat.com/~lcapitul/real-time/acct-bug.c All of them reproduce the issue 100% of the time for me.
#define _GNU_SOURCE #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <sched.h> #include <sys/types.h> static int move_to_cpu(int cpu) { cpu_set_t set; CPU_ZERO(&set); CPU_SET(cpu, &set); return sched_setaffinity(0, sizeof(set), &set); } static void loop(void) { for (;;) ; } static int fork_hog(int cpu) { int pid; pid = (int) fork(); if (pid == 0) { move_to_cpu(cpu); loop(); exit(0); } return pid; } int main(int argc, char *argv[]) { int i, pid, cpu, nr_procs; if (argc != 3) { printf("usage: hog < nr-procs > < CPU >\n"); exit(1); } cpu = atoi(argv[2]); nr_procs = atoi(argv[1]); for (i = 0; i < nr_procs; i++) { pid = fork_hog(cpu); fprintf(stderr, "created hog%d pid=%d\n", i, pid); } fprintf(stderr, "pausing...\n"); pause(); return 0; }