Add tool "cachestats" to print out the cache map

Makefile

 default:
+	gcc -Wall -o cachestats cachestats.c
 	gcc -Wall -fPIC -c -o nocache.o nocache.c
 	gcc -Wall -fPIC -c -o fcntl_helpers.o fcntl_helpers.c
 	gcc -Wall -shared -Wl,-soname,nocache.so.1 -ldl -o nocache.so nocache.o fcntl_helpers.o

cachestats.c

+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <error.h>
+#include <stdio.h>
+
+int exiterr(const char *s)
+{
+    perror(s);
+    exit(-1);
+}
+
+int main(int argc, char *argv[])
+{
+    int i, j;
+    int pages;
+    int PAGESIZE;
+
+    int quiet = 0;
+    int verbose = 0;
+
+    int fd;
+    struct stat st;
+    void *file = NULL;
+    unsigned char *pageinfo = NULL;
+
+    PAGESIZE = getpagesize();
+
+    if(argc > 1) {
+        if(!strcmp("-v", argv[1]))
+            verbose = 1;
+        else if(!strcmp("-q", argv[1]))
+            quiet = 1;
+    } else {
+        fprintf(stderr, "usage: %s [-qv] <file> "
+            "-- print out cache statistics\n", argv[0]);
+        fprintf(stderr, "\t-v\tprint verbose cache map\n");
+        fprintf(stderr, "\t-q\texit code tells if file is fully cached\n");
+        exit(1);
+    }
+
+    if(quiet || verbose)
+        argv++;
+
+    fd = open(argv[1], O_RDONLY);
+    if(fd == -1)
+        exiterr("open");
+
+    if(fstat(fd, &st) == -1)
+        exiterr("fstat");
+    if(!S_ISREG(st.st_mode)) {
+        fprintf(stderr, "%s: S_ISREG: not a regular file", argv[1]);
+        return EXIT_FAILURE;
+    }
+    if(st.st_size == 0) {
+        fprintf(stderr, "%s: file size is 0!\n", argv[1]);
+        return EXIT_FAILURE;
+    }
+
+    pages = (st.st_size + PAGESIZE - 1) / PAGESIZE;
+    pageinfo = calloc(sizeof(*pageinfo), pages);
+    if(!pageinfo)
+        exiterr("calloc");
+
+    file = mmap(NULL, st.st_size, PROT_NONE, MAP_SHARED, fd, 0);
+    if(file == MAP_FAILED)
+        exiterr("mmap");
+    if(mincore(file, st.st_size, pageinfo) == -1)
+        exiterr("mincore");
+
+    i = j = 0;
+    while(i < pages)
+        if(pageinfo[i++] & 1)
+            j++;
+
+    if(quiet) {
+        if(j == i)
+            return EXIT_SUCCESS;
+        return EXIT_FAILURE;
+    }
+
+    printf("pages in cache: %d/%d (%.1f%%)\n", j, i, 100.0 * j / i);
+
+#define PAGES_PER_LINE 16
+    if(verbose) {
+        printf("\ncache map:\n");
+        for(i = 0; i <= (pages - 1) / PAGES_PER_LINE; i++) {
+            printf("%6d: |", i);
+            for(j = 0; j < PAGES_PER_LINE; j++) {
+                printf("%c|",
+                    pageinfo[i * PAGES_PER_LINE + j] & 1 ? 'x' : ' ');
+            }
+            printf("\n");
+        }
+    }
+
+    munmap(file, st.st_size);
+    return EXIT_SUCCESS;
+}