On Fri, Oct 12, 2018 at 11:26:30AM -0700, Solio Sarabia wrote:
> Hi --
>
> turbostat 17.06.23 is throwing an exception on a custom linux-4.16.12
> kernel, on Xeon E5-2699 v4 Broadwell EP, 2S, 22C/S, 44C total, HT off,
> VTx off.
>
> Initially the system had 4.4.0-137. Then I built and installed
> linux-4.16.12-default. turbostat works fine for these two versions.
> After building linux-4.16.12 for a second time, the older kernel is
> renamed and now `ls -l /boot/` (I'm using version without .old suffix):
>
> vmlinuz-4.16.12-default+
> vmlinuz-4.16.12-default+.old
>
> grep -i 'turbostat' /var/log/kern.log
>
> kernel: [ 159.140836] capability: warning: `turbostat' uses 32-bit
> capabilities (legacy support in use)
> kernel: [ 164.149264] traps: turbostat[1801] trap divide error
> ip:407625 sp:7ffe4b0df000 error:0 in turbostat[400000+17000]
>
> (gdb)
> cpu22: MSR_PKGC3_IRTL: 0x00000000 (NOTvalid, 0 ns)
> cpu22: MSR_PKGC6_IRTL: 0x00000000 (NOTvalid, 0 ns)
> cpu22: MSR_PKGC7_IRTL: 0x00000000 (NOTvalid, 0 ns)
>
> Program received signal SIGFPE, Arithmetic exception.
> 0x0000000000407625 in compute_average (t=0x61a3b0, c=0x61a3d0, p=0x61a480) at turbostat.c:1378
> 1378 average.threads.tsc /= topo.num_cpus;
>
Why would the cpu topology report 0 cpus? I added a debug entry to
cpu_usage_stat and /proc/stat showed it as an extra column. Then
fscanf parsing in for_all_cpus() failed, causing the SIGFPE.
This is not an issue. Thanks.
> Let me know if you need more details.
>
> Thanks,
> -SS
> Why would the cpu topology report 0 cpus? I added a debug entry to
> cpu_usage_stat and /proc/stat showed it as an extra column. Then
> fscanf parsing in for_all_cpus() failed, causing the SIGFPE.
>
> This is not an issue. Thanks.
Yes, it is true that turbostat doesn't check for systems with 0 cpus.
I'm curious how you provoked the kernel to claim that. If it is
something others might do, we can have check for it and gracefully
exit.
thanks,
-Len
--
Len Brown, Intel Open Source Technology Center
On Fri, Oct 12, 2018 at 07:03:41PM -0400, Len Brown wrote:
> > Why would the cpu topology report 0 cpus? I added a debug entry to
> > cpu_usage_stat and /proc/stat showed it as an extra column. Then
> > fscanf parsing in for_all_cpus() failed, causing the SIGFPE.
> >
> > This is not an issue. Thanks.
>
> Yes, it is true that turbostat doesn't check for systems with 0 cpus.
> I'm curious how you provoked the kernel to claim that. If it is
> something others might do, we can have check for it and gracefully
> exit.
source/tools/power/x86/turbostat/turbostat.c
int for_all_proc_cpus(int (func)(int))
{
retval = fscanf(fp, "cpu %*d %*d %*d %*d %*d %*d %*d %*d %*d %*d\n");
^
This fails due to an extra debug entry in /proc/stat
(total of 11 columns). I was measuring time in a hot
function and decided to add this time in an extra
cpu_usage_stat. This was an experiment though.
Thanks,
-S.