tools/power: turbostat: fix large c1% issue

Under some conditions, c1% was displayed as very large number,
much higher than 100%.

c1% is not measured, it is derived as "that, which is left over"
from other counters.  However, the other counters are not collected
atomically, and so it is possible for c1% to be calaculagted as
a small negative number -- displayed as very large positive.

There was a check for mperf vs tsc for this already,
but it needed to also include the other counters
that are used to calculate c1.

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 b815a12159b28126d7c698af687965498305f623..861d771902065877ee0e09deb50adcde31b534fc 100644 (file)
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -444,6 +444,9 @@ delta_core(struct core_data *new, struct core_data *old)
        old->c7 = new->c7 - old->c7;
 }
 
+/*
+ * old = new - old
+ */
 void
 delta_thread(struct thread_data *new, struct thread_data *old,
        struct core_data *core_delta)
@@ -482,19 +485,20 @@ delta_thread(struct thread_data *new, struct thread_data *old,
 
 
        /*
-        * As mperf and tsc collection are not atomic,
-        * it is possible for mperf's non-halted cycles
+        * As counter collection is not atomic,
+        * it is possible for mperf's non-halted cycles + idle states
         * to exceed TSC's all cycles: show c1 = 0% in that case.
         */
-       if (old->mperf > old->tsc)
+       if ((old->mperf + core_delta->c3 + core_delta->c6 + core_delta->c7) > old->tsc)
                old->c1 = 0;
        else {
                /* normal case, derive c1 */
                old->c1 = old->tsc - old->mperf - core_delta->c3
                                - core_delta->c6 - core_delta->c7;
        }
+
        if (old->mperf == 0) {
-               if (verbose) fprintf(stderr, "cpu%d MPERF 0!\n", old->cpu_id);
+               if (verbose > 1) fprintf(stderr, "cpu%d MPERF 0!\n", old->cpu_id);
                old->mperf = 1; /* divide by 0 protection */
        }