gdb/testsuite/gdb.trace/tspeed.c

   1 /* This testcase is part of GDB, the GNU debugger.
   2
   3    Copyright 2010-2024 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* This program tests tracepoint speed. It consists of two identical
  19    loops, which in normal execution will run for exactly the same
  20    amount of time. A tracepoint in the second loop will slow it down
  21    by some amount, and then the program will report the slowdown
  22    observed.  */
  23
  24 /* While primarily designed for the testsuite, it can also be used
  25    for interactive testing.  */
  26
  27 #include <stdio.h>
  28 #include <time.h>
  29 #include <sys/time.h>
  30 #include <sys/resource.h>
  31 #include <unistd.h>
  32
  33 int trace_speed_test (void);
  34
  35 /* We mark these globals as volatile so the speed-measuring loops
  36    don't get totally emptied out at high optimization levels.  */
  37
  38 volatile int globfoo, globfoo2, globfoo3;
  39
  40 volatile short globarr[80000];
  41
  42 int init_iters = 10 * 1000;
  43
  44 int iters;
  45
  46 int max_iters = 1000 * 1000 * 1000;
  47
  48 int numtps = 1;
  49
  50 unsigned long long now2, now3, now4, now5;
  51 int total1, total2, idelta, mindelta, nsdelta;
  52 int nspertp = 0;
  53
  54 /* Return CPU usage (both user and system - trap-based tracepoints use
  55    a bunch of system time).  */
  56
  57 unsigned long long
  58 myclock ()
  59 {
  60   struct timeval tm;
  61   gettimeofday (&tm, NULL);
  62   return (((unsigned long long) tm.tv_sec) * 1000000) + tm.tv_usec;
  63 }
  64
  65 int
  66 main(int argc, char **argv)
  67 {
  68   int problem;
  69
  70   iters = init_iters;
  71
  72   while (1)
  73     {
  74       numtps = 1;  /* set pre-run breakpoint here */
  75
  76       /* Keep trying the speed test, with more iterations, until
  77          we get to a reasonable number.  */
  78       while ((problem = trace_speed_test()))
  79         {
  80           /* If iteration isn't working, give up.  */
  81           if (iters > max_iters)
  82             {
  83               printf ("Gone over %d iterations, giving up\n", max_iters);
  84               break;
  85             }
  86           if (problem < 0)
  87             {
  88               printf ("Negative times, giving up\n");
  89               break;
  90             }
  91
  92           iters *= 2;
  93           printf ("Doubled iterations to %d\n", iters);
  94         }
  95
  96       printf ("Tracepoint time is %d ns\n", nspertp);
  97
  98       /* This is for the benefit of interactive testing and attaching,
  99          keeps the program from pegging the machine.  */
 100       sleep (1);  /* set post-run breakpoint here */
 101
 102       /* Issue a little bit of output periodically, so we can see if
 103          program is alive or hung.  */
 104       printf ("%s keeping busy, clock=%llu\n", argv[0], myclock ());
 105     }
 106   return 0;
 107 }
 108
 109 int
 110 trace_speed_test (void)
 111 {
 112   int i;
 113
 114   /* Overall loop run time deltas under 1 ms are likely noise and
 115      should be ignored.  */
 116   mindelta = 1000;
 117
 118   // The bodies of the two loops following must be identical.
 119
 120   now2 = myclock ();
 121   globfoo2 = 1;
 122   for (i = 0; i < iters; ++i)
 123     {
 124       globfoo2 *= 45;
 125       globfoo2 += globfoo + globfoo3;
 126       globfoo2 *= globfoo + globfoo3;
 127       globfoo2 -= globarr[4] + globfoo3;
 128       globfoo2 *= globfoo + globfoo3;
 129       globfoo2 += globfoo + globfoo3;
 130     }
 131   now3 = myclock ();
 132   total1 = now3 - now2;
 133
 134   now4 = myclock ();
 135   globfoo2 = 1;
 136   for (i = 0; i < iters; ++i)
 137     {
 138       globfoo2 *= 45;
 139       globfoo2 += globfoo + globfoo3;  /* set tracepoint here */
 140       globfoo2 *= globfoo + globfoo3;
 141       globfoo2 -= globarr[4] + globfoo3;
 142       globfoo2 *= globfoo + globfoo3;
 143       globfoo2 += globfoo + globfoo3;
 144     }
 145   now5 = myclock ();
 146   total2 = now5 - now4;
 147
 148   /* Report on the test results.  */
 149
 150   nspertp = 0;
 151
 152   idelta = total2 - total1;
 153
 154   printf ("Loops took %d usec and %d usec, delta is %d usec, %d iterations\n",
 155           total1, total2, idelta, iters);
 156
 157   /* If the second loop seems to run faster, things are weird so give up.  */
 158   if (idelta < 0)
 159     return -1;
 160
 161   if (idelta > mindelta
 162       /* Total test time should be between 15 and 30 seconds.  */
 163       && (total1 + total2) > (15 * 1000000)
 164       && (total1 + total2) < (30 * 1000000))
 165     {
 166       nsdelta = (((unsigned long long) idelta) * 1000) / iters;
 167       printf ("Second loop took %d ns longer per iter than first\n", nsdelta);
 168       nspertp = nsdelta / numtps;
 169       printf ("%d ns per tracepoint\n", nspertp);
 170       printf ("Base iteration time %d ns\n",
 171               ((int) (((unsigned long long) total1) * 1000) / iters));
 172       printf ("Total test time %d secs\n", ((int) ((now5 - now2) / 1000000)));
 173
 174       /* Speed test ran with no problem.  */
 175       return 0;
 176     }
 177
 178   /* The test run was too brief, or otherwise not useful.  */
 179   return 1;
 180 }