1 /*- 2 * Copyright (c) 2006, Stephan Uphoff <ups@freebsd.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice unmodified, this list of conditions, and the following 10 * disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 28 #include <sys/types.h> 29 #include <unistd.h> 30 #include <sys/stat.h> 31 #include <fcntl.h> 32 #include <stdio.h> 33 #include <stdlib.h> 34 #include <sys/mman.h> 35 36 37 int prepareFile(const char* filename,int* fdp); 38 int mapBuffer(char** bufferp,int fd1,int fd2); 39 int startIO(int fd,char *buffer); 40 41 static int pagesize; 42 43 #define FILESIZE (32*1024) 44 static char wbuffer[FILESIZE]; 45 46 /* Create a FILESIZE sized file - then remove file data from the cache*/ 47 int prepareFile(const char* filename,int* fdp) 48 { 49 int fd; 50 int len; 51 int status; 52 void *addr; 53 54 fd = open(filename,O_CREAT | O_TRUNC | O_RDWR,S_IRWXU); 55 if (fd == -1) 56 { 57 perror("Creating file"); 58 return fd; 59 } 60 61 len = write(fd,wbuffer,FILESIZE); 62 if (len < 0) 63 { 64 perror("Write failed"); 65 return 1; 66 } 67 68 status = fsync(fd); 69 if (status != 0) 70 { 71 perror("fsync failed"); 72 return 1; 73 } 74 75 addr = mmap(NULL,FILESIZE, PROT_READ | PROT_WRITE , MAP_SHARED, fd, 0); 76 if (addr == MAP_FAILED) 77 { 78 perror("Mmap failed"); 79 return 1; 80 } 81 82 status = msync(addr,FILESIZE,MS_INVALIDATE | MS_SYNC); 83 if (status != 0) 84 { 85 perror("Msync failed"); 86 return 1; 87 } 88 89 munmap(addr,FILESIZE); 90 91 *fdp = fd; 92 return 0; 93 } 94 95 96 /* mmap a 2 page buffer - first page is from fd1, second page from fd2 */ 97 int mapBuffer(char** bufferp,int fd1,int fd2) 98 { 99 void* addr; 100 char *buffer; 101 102 addr = mmap(NULL,pagesize*2, PROT_READ | PROT_WRITE , MAP_SHARED, fd1, 0); 103 if (addr == MAP_FAILED) 104 { 105 perror("Mmap failed"); 106 return 1; 107 } 108 109 buffer = addr; 110 addr = mmap(buffer + pagesize,pagesize, PROT_READ | PROT_WRITE , MAP_FIXED | 111 MAP_SHARED, fd2, 0); 112 113 if (addr == MAP_FAILED) 114 { 115 perror("Mmap2 failed"); 116 return 1; 117 } 118 *bufferp = buffer; 119 return 0; 120 } 121 122 123 int startIO(int fd,char *buffer) 124 { 125 ssize_t len; 126 len = write(fd,buffer,2*pagesize); 127 if (len == -1) 128 { 129 perror("write failed"); 130 return 1; 131 } 132 return 0; 133 } 134 135 136 int main(int argc __unused, char *argv[] __unused) 137 { 138 139 int fdA,fdB,fdDelayA,fdDelayB; 140 int status; 141 char *bufferA,*bufferB; 142 pid_t pid; 143 144 pagesize = getpagesize(); 145 146 if ((prepareFile("A",&fdA)) 147 || (prepareFile("B",&fdB)) 148 || (prepareFile("DelayA",&fdDelayA)) 149 || (prepareFile("DelayB",&fdDelayB)) 150 || (mapBuffer(&bufferA,fdDelayA,fdB)) 151 || (mapBuffer(&bufferB,fdDelayB,fdA))) 152 exit(1); 153 154 pid = fork(); 155 156 if (pid == 0) 157 { 158 status = startIO(fdA,bufferA); 159 exit(status); 160 } 161 162 if (pid == -1) 163 { 164 exit(1); 165 } 166 status = startIO(fdB,bufferB); 167 exit(status); 168 169 } 170 171 172 173 174 175