xenpm: Fix reporting of C0 residence times

Idle state residence times as provided by pmstat_get_cx_stat() are not
reported precisely since remote core may be in idle state and
therefore has not updated its statistics at the time local core
collected them.  This causes C0 residencies as calculated by xenpm to
sometimes become negative.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@amd.com>
Committed-by: Keir Fraser <keir@xen.org>

diff --git a/tools/misc/xenpm.c b/tools/misc/xenpm.c
index f07a53967f2efceb460d64ebf87ba69495fb8113..65876fe370922b54f9fa8bcc9ddcfcde03fb7dff 100644 (file)
--- a/tools/misc/xenpm.c
+++ b/tools/misc/xenpm.c
@@ -351,8 +351,12 @@ static void signal_int_handler(int signo)
         for ( i = 0; i < max_cpu_nr; i++ )
             if ( !get_cxstat_by_cpuid(xc_handle, i, &cxstat_end[i]) )
                 for ( j = 0; j < cxstat_end[i].nr; j++ )
-                    sum_cx[i] += cxstat_end[i].residencies[j] -
-                                 cxstat_start[i].residencies[j];
+                {
+                    int64_t diff = (int64_t)cxstat_end[i].residencies[j] -
+                        (int64_t)cxstat_start[i].residencies[j];
+                    if ( diff >=0 )
+                        sum_cx[i] += diff;
+                }
     }
 
     if ( get_pxstat_by_cpuid(xc_handle, 0, NULL) != -ENODEV )
@@ -379,8 +383,10 @@ static void signal_int_handler(int signo)
         {
             for ( j = 0; j < cxstat_end[i].nr; j++ )
             {
-                res = cxstat_end[i].residencies[j] -
-                    cxstat_start[i].residencies[j];
+                int64_t diff = (int64_t)cxstat_end[i].residencies[j] -
+                    (int64_t)cxstat_start[i].residencies[j];
+
+                res = ( diff >= 0 ) ? diff : 0;
                 triggers = cxstat_end[i].triggers[j] -
                     cxstat_start[i].triggers[j];
                 avg_res = (triggers==0) ? 0: (double)res/triggers/1000000.0;