* Stanislaw Gruszka <sgrus...@redhat.com> wrote: > Scaling cputime cause problems, bunch of them was fixed, but still is > possible > to hit multiplication overflow issue, which make {u,s}time values incorrect. > This problem has no good solution in kernel.
Wasn't 128-bit math a solution to the overflow problems? 128-bit math isn't nice, but at least for multiplication it's defensible. > This patch remove scaling code and export raw values of {u,t}ime . Procps > programs can use newly introduced sum_exec_runtime to find out precisely > calculated process cpu time and scale utime, stime values accordingly. > > Unfortunately times(2) syscall has no such option. > > This change affect kernels compiled without CONFIG_VIRT_CPU_ACCOUNTING_*. So, the concern here is that 'top hiding' code can now hide again. It's also that we are not really solving the problem, we are pushing it to user-space - which in the best case gets updated to solve the problem in some similar fashion - and in the worst case does not get updated or does it in a buggy way. So while user-space has it a bit easier because it can do floating point math, is there really no workable solution to the current kernel side integer overflow bug? I really prefer robust kernel side accounting/instrumentation. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/