tools/power turbostat: fix bogus summary values

This patch fixes a regression introduced in

commit 8cb48b32a5de ("tools/power turbostat: track thread ID in cpu_topology")

Turbostat uses incorrect cores number ('topo.num_cores') - its value is count
of logical CPUs, instead of count of physical cores. So it is twice as large as
it should be on a typical Intel system. For example, on a 6 core Xeon system
'topo.num_cores' is 12, and on a 52 core Xeon system 'topo.num_cores' is 104.

And interestingly, on a 68-core Knights Landing Intel system 'topo.num_cores'
is 272, because this system has 4 logical CPUs per core.

As a result, some of the turbostat calculations are incorrect. For example,
on idle 52-core Xeon system when all cores are ~99% in Core C6 (CPU%c6), the
summary (very first) line shows ~48% Core C6, while it should be ~99%.

This patch fixes the problem by fixing 'topo.num_cores' calculation.

Was:

1. Init 'thread_id' for all CPUs to -1
2. Run 'get_thread_siblings()' which sets it to 0 or 1
3. Increment 'topo.num_cores' when thread_id != -1 (bug!)

Now:

1. Init 'thread_id' for all CPUs to -1
2. Run 'get_thread_siblings()' which sets it to 0 or 1
3. Increment 'topo.num_cores' when thread_id is not 0

I did not have a chance to test this on an AMD machine, and only tested on a
couple of Intel Xeons (6 and 52 cores).

Reported-by: Vladislav Govtva <vladislav.govtva@intel.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index 81a1df0..1b53a24 100644 (file)
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -4838,7 +4838,7 @@ void topology_probe()
                siblings = get_thread_siblings(&cpus[i]);
                if (siblings > max_siblings)
                        max_siblings = siblings;
-               if (cpus[i].thread_id != -1)
+               if (cpus[i].thread_id == 0)
                        topo.num_cores++;
 
                if (debug > 1)