test/sysperf/mutex3.c

   1 /*
   2  * mutex3.c
   3  *
   4  * $DragonFly: src/test/sysperf/mutex3.c,v 1.1 2006/05/18 04:22:46 dillon Exp $
   5  */
   6
   7 #include "blib.h"
   8
   9 #include <sys/types.h>
  10 #include <machine/atomic.h>
  11 #include <machine/cpufunc.h>
  12
  13 int *mtx;
  14 int refcnt;
  15
  16 static void
  17 spin_lock_contested(void)
  18 {
  19         int i;
  20         int j;
  21
  22         j = 1;
  23         while (atomic_swap_int(mtx, 1) != 0) {
  24                 for (i = 0; i < j; ++i)
  25                         __asm __volatile("pause"::);
  26                 j <<= 1;
  27         }
  28 }
  29
  30 static __inline void
  31 spin_lock(void)
  32 {
  33         if (refcnt == 1) {
  34                 if (*mtx == 0)
  35                         *mtx = 1;
  36                 else
  37                         spin_lock_contested();
  38         } else if (atomic_swap_int(mtx, 1) != 0) {
  39                 spin_lock_contested();
  40         }
  41 }
  42
  43 static __inline void
  44 spin_unlock(void)
  45 {
  46         cpu_sfence();
  47         *mtx = 0;
  48 }
  49
  50 int
  51 main(int ac, char **av)
  52 {
  53     long long count = 0;
  54     long long max;
  55     int j;
  56     int *counter;
  57     pid_t pid;
  58
  59     printf("Test simple locked bus cycle mutex latency\n");
  60     printf("auto-forks two processes for the test with shared memory\n");
  61     printf("This test is only useful on a SMP box\n");
  62
  63     start_timing();
  64     mtx = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANON, -1, 0);
  65     counter = mtx + 64;
  66     while (stop_timing(0, NULL) == 0) {
  67         for (j = 0; j < 100; ++j) {
  68             spin_lock();
  69             spin_unlock();
  70         }
  71         count += 100;
  72     }
  73     max = count;
  74     *mtx = 0;
  75
  76     refcnt = 1;
  77     start_timing();
  78     for (count = 0; count < max; count += 100) {
  79         for (j = 0; j < 100; ++j) {
  80             spin_lock();
  81             spin_unlock();      /* release */
  82             ++counter[64];
  83         }
  84     }
  85     stop_timing(count, "complex_mtx(uncontested/1cpu)");
  86     refcnt = 2;
  87
  88     if ((pid = fork()) == 0) {
  89         for (;;) {
  90             for (j = 0; j < 100; ++j) {
  91                 spin_lock();
  92                 spin_unlock();  /* release */
  93                 ++counter[128];
  94             }
  95         }
  96     } else {
  97         start_timing();
  98         for (count = 0; count < max; count += 100) {
  99             for (j = 0; j < 100; ++j) {
 100                 spin_lock();
 101                 spin_unlock();  /* release */
 102                 ++counter[64];
 103             }
 104         }
 105         stop_timing(count, "complex_mtx");
 106         printf("proc1=%d proc2=%d\n", counter[64], counter[128]);
 107         kill(pid, 9);
 108     }
 109     return(0);
 110 }
 111