vmem/memlock.c

+/* memlock.c
+
+   Demonstrate the use of mlock(), to place memory locks, and mincore(), to
+   retrieve memory-residence information about the calling processes virtual
+   memory pages.
+
+   Note: some UNIX implementations do not provide mincore().
+
+   The madvise() system call is supported on Linux since kernel 2.4.
+*/
 #define _BSD_SOURCE             /* Get mincore() declaration and MAP_ANONYMOUS
                                    definition from <sys/mman.h> */
 #include <sys/mman.h>
 #include "tlpi_hdr.h"
 
 /* Display residency of pages in range [addr .. (addr + length - 1)] */
 
 static void
 displayMincore(char *addr, size_t length)
 {
     unsigned char *vec;
     long pageSize, numPages, j;
 
+#ifndef _SC_PAGESIZE
+    pageSize = getpagesize();   /* Some systems don't have _SC_PAGESIZE */
+#else
     pageSize = sysconf(_SC_PAGESIZE);
+#endif
 
     numPages = (length + pageSize - 1) / pageSize;
     vec = malloc(numPages);
     if (vec == NULL)
         errExit("malloc");
 
     if (mincore(addr, length, vec) == -1)
         errExit("mincore");
 
     for (j = 0; j < numPages; j++) {
         if (j % 64 == 0)
             printf("%s%10p: ", (j == 0) ? "" : "\n", addr + (j * pageSize));
         printf("%c", (vec[j] & 1) ? '*' : '.');
     }
     printf("\n");
 
     free(vec);
 }
 
 int
 main(int argc, char *argv[])
 {
     char *addr;
     size_t len, lockLen;
     long pageSize, stepSize, j;
 
     if (argc != 4 || strcmp(argv[1], "--help") == 0)
         usageErr("%s num-pages lock-page-step lock-page-len\n", argv[0]);
 
+#ifndef _SC_PAGESIZE
+    pageSize = getpagesize();
+    if (pageSize == -1)
+        errExit("getpagesize");
+#else
     pageSize = sysconf(_SC_PAGESIZE);
     if (pageSize == -1)
         errExit("sysconf(_SC_PAGESIZE)");
+#endif
 
     len =      getInt(argv[1], GN_GT_0, "num-pages") * pageSize;
     stepSize = getInt(argv[2], GN_GT_0, "lock-page-step") * pageSize;
     lockLen =  getInt(argv[3], GN_GT_0, "lock-page-len") * pageSize;
 
     addr = mmap(NULL, len, PROT_READ, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
     if (addr == MAP_FAILED)
         errExit("mmap");
 
     printf("Allocated %ld (%#lx) bytes starting at %p\n",
             (long) len, (unsigned long) len, addr);
 
     printf("Before mlock:\n");
     displayMincore(addr, len);
 
     /* Lock pages specified by command-line arguments into memory */
 
     for (j = 0; j + lockLen <= len; j += stepSize)
         if (mlock(addr + j, lockLen) == -1)
             errExit("mlock");
 
     printf("After mlock:\n");
     displayMincore(addr, len);
 
     exit(EXIT_SUCCESS);
 }