src/jdk.management/linux/native/libmanagement_ext/UnixOperatingSystem.c did not properly initialize counters.jvmTicks an counters.cpuTicks in perfInit() method. Function get_cpuload_internal(...) calls get_totalticks() and get_jvmticks() functions that update these counters. But on the first call, it used to compare the newly received counters with the garbage.

The missed initialization was fixed in JDK-8226575, however, there is a code in get_cpuload_internal(...) method that seems to be written to somehow mitigate the missed initialization and in worse case just return 0 or 1.0. But it also could be that there is some other problem this code tries to solve. This issue is filed to look into this and remove these workarounds.

    // seems like we sometimes end up with less kernel ticks when
    // reading /proc/self/stat a second time, timing issue between cpus?
    if (pticks->usedKernel < tmp.usedKernel) {
        kdiff = 0;
    } else {
        kdiff = pticks->usedKernel - tmp.usedKernel;
    }
    tdiff = pticks->total - tmp.total;
    udiff = pticks->used - tmp.used;
    
    if (tdiff == 0) {
        user_load = 0;
    } else {
        if (tdiff < (udiff + kdiff)) {
            tdiff = udiff + kdiff;
        }
        *pkernelLoad = (kdiff / (double)tdiff);
        // BUG9044876, normalize return values to sane values
        *pkernelLoad = MAX(*pkernelLoad, 0.0);
        *pkernelLoad = MIN(*pkernelLoad, 1.0);
        
        user_load = (udiff / (double)tdiff);
        user_load = MAX(user_load, 0.0);
        user_load = MIN(user_load, 1.0);
    }