avutil/timer: show histogram of cpu cycles each run took

The new information is printed at verbose log level and can thus be switched on and off
through the log level
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavutil/timer.h

@@ -69,6 +69,8 @@
         static uint64_t tsum   = 0;                                       \
         static int tcount      = 0;                                       \
         static int tskip_count = 0;                                       \
+        static int thistogram[32] = {0};                                  \
+        thistogram[av_log2(tend - tstart)]++;                             \
         if (tcount < 2                        ||                          \
             tend - tstart < 8 * tsum / tcount ||                          \
             tend - tstart < 2000) {                                       \
@@ -77,9 +79,13 @@
         } else                                                            \
             tskip_count++;                                                \
         if (((tcount + tskip_count) & (tcount + tskip_count - 1)) == 0) { \
+            int i;                                                        \
             av_log(NULL, AV_LOG_ERROR,                                    \
-                   "%"PRIu64" " FF_TIMER_UNITS " in %s, %d runs, %d skips\n",          \
+                   "%"PRIu64" " FF_TIMER_UNITS " in %s, %d runs, %d skips",          \
                    tsum * 10 / tcount, id, tcount, tskip_count);          \
+            for (i = 0; i < 32; i++)                                      \
+                av_log(NULL, AV_LOG_VERBOSE, " %2d", av_log2(2*thistogram[i]));\
+            av_log(NULL, AV_LOG_ERROR, "\n");                             \
         }                                                                 \
     }
 #else