1#define _GNU_SOURCE
2#include <string.h>
3#include <pthread.h>
4#include <stdlib.h>
5#include <stdio.h>
6#include <unistd.h>
7#include <sys/types.h>
8
9// memrw provides a simulation of an application
10// reading and writing memory, for the sake of tuning helgrind.
11// It is a very simple (simplistic) model:
12//  * only one thread
13//  * only one exe context reading or writing the memory
14//  * the working set of the application is unrealistically
15//    concentrated on a consecutive nr of MB.
16// At this moment, it was just used to tune the EvM data structure
17// of helgrind.
18// It would be nice to enhance this program to cope with a richer
19// model e.g. multiple threads, many different stack traces touching
20// the memory, better working set distribution, ...
21
22static int sz_b; // size of a block
23static int nr_b; // total nr of blocks used by the program
24static int nr_b_ws; // nr_b in program working set
25static int nr_loops; // nr of loops reading or writing the ws
26static int nr_thr; // nr of threads (hardcoded to 1 currently)
27static int nr_repeat; // nr of times we will allocate, use, then free total+ws
28
29// Note: the total nr of MB is what is explicitly allocated.
30// On top of that, we have the stacks, local vars, lib vars, ...
31// The working set is just the first nr_b_ws blocks of nr_b.
32
33static int verbose = 0;
34static unsigned char **t_b; // Pointers to all blocks
35
36static void *memrw_fn(void *v)
37{
38   int loops, m, b;
39   int dowrite;
40   int differs = 0;
41   unsigned char prev = 0;
42
43   for (loops = 0; loops < nr_loops; loops++) {
44      // printf("loop %d dowrite %d\n", loops, dowrite);
45      // Note: in case of multiple threads, we will have
46      // to add lock/unlock somewhere in the below, maybe to lock
47      // the MB we are reading or writing.
48      for (m = 0; m < nr_b_ws; m++) {
49         for (b = 0; b < sz_b; b++) {
50            dowrite = b % 5 == 0;
51            // Do some write or read operations.
52            if (dowrite) {
53               if (t_b[m][b] < 255)
54                  t_b[m][b] += differs;
55               else
56                  t_b[m][b] = 0;
57            } else {
58               differs = t_b[m][b] != prev;
59               prev = t_b[m][b];
60            }
61         }
62      }
63   }
64   return NULL;
65}
66
67int main (int argc, char *argv[])
68{
69   int a;
70   int ret;
71   int i;
72   int r;
73   pthread_t thr;
74
75   // usage: memrw [-b blocksize default 1MB ]
76   //              [-t nr_b default 10] [-w nr_b_ws default 10]
77   //              [-l nr_loops_on_ws default 3]
78   //              [-r nr_repeat default 1]
79   //              [-f fan_out default 0]
80   //              [-v verbosity default 0]
81   sz_b = 1024 * 1024;
82   nr_b = 10;
83   nr_b_ws = 10;
84   nr_loops = 3;
85   nr_repeat = 1;
86   verbose = 0;
87   for (a = 1; a < argc; a+=2) {
88      if        (strcmp(argv[a], "-b") == 0) {
89         sz_b = atoi(argv[a+1]);
90      } else if (strcmp(argv[a], "-t") == 0) {
91         nr_b = atoi(argv[a+1]);
92      } else if (strcmp(argv[a], "-w") == 0) {
93         nr_b_ws = atoi(argv[a+1]);
94      } else if (strcmp(argv[a], "-l") == 0) {
95         nr_loops = atoi(argv[a+1]);
96      } else if (strcmp(argv[a], "-r") == 0) {
97         nr_repeat = atoi(argv[a+1]);
98      } else if (strcmp(argv[a], "-v") == 0) {
99         verbose = atoi(argv[a+1]);
100      } else {
101         printf("unknown arg %s\n", argv[a]);
102      }
103   }
104   if (nr_b_ws > nr_b)
105      nr_b_ws = nr_b; // to make it easy to do loops combining values
106
107   nr_thr = 1;
108
109   printf ("total program memory -t %llu MB"
110           " working set -w %llu MB\n",
111           ((unsigned long long)nr_b * sz_b)
112             / (unsigned long long) (1024*1024),
113           ((unsigned long long)nr_b_ws * sz_b)
114             / (unsigned long long)(1024*1024));
115   printf (" working set R or W -l %d times"
116           " repeat the whole stuff -r %d times\n",
117           nr_loops,
118           nr_repeat);
119
120   for (r = 0; r < nr_repeat; r++) {
121      printf ("creating and initialising the total program memory\n");
122      t_b = malloc(nr_b * sizeof(char*));
123      if (t_b == NULL)
124         perror("malloc t_b");
125      for (i = 0; i < nr_b; i++) {
126         t_b[i] = calloc(sz_b, 1);
127         if (t_b[i] == NULL)
128            perror("malloc t_b[i]");
129      }
130
131      printf("starting thread that will read or write the working set\n");
132      ret = pthread_create(&thr, NULL, memrw_fn, &nr_thr);
133      if (ret != 0)
134         perror("pthread_create");
135      printf("waiting for thread termination\n");
136
137      ret = pthread_join(thr, NULL);
138      if (ret != 0)
139         perror("pthread_join");
140      printf("thread terminated\n");
141
142      /* Now, free the memory used, for the next repeat */
143      for (i = 0; i < nr_b; i++)
144         free (t_b[i]);
145      free (t_b);
146      printf("memory freed\n");
147   }
148
149   return 0;
150}
151