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 * $FreeBSD$ 27 */ 28 29 30 #include <sys/types.h> 31 #include <unistd.h> 32 #include <sys/stat.h> 33 #include <fcntl.h> 34 #include <stdio.h> 35 #include <stdlib.h> 36 #include <sys/mman.h> 37 38 39 int prepareFile(const char* filename,int* fdp); 40 int mapBuffer(char** bufferp,int fd1,int fd2); 41 int startIO(int fd,char *buffer); 42 43 static int pagesize; 44 45 #define FILESIZE (32*1024) 46 static char wbuffer[FILESIZE]; 47 48 /* Create a FILESIZE sized file - then remove file data from the cache*/ 49 int prepareFile(const char* filename,int* fdp) 50 { 51 int fd; 52 int len; 53 int status; 54 void *addr; 55 56 fd = open(filename,O_CREAT | O_TRUNC | O_RDWR,S_IRWXU); 57 if (fd == -1) 58 { 59 perror("Creating file"); 60 return fd; 61 } 62 63 len = write(fd,wbuffer,FILESIZE); 64 if (len < 0) 65 { 66 perror("Write failed"); 67 return 1; 68 } 69 70 status = fsync(fd); 71 if (status != 0) 72 { 73 perror("fsync failed"); 74 return 1; 75 } 76 77 addr = mmap(NULL,FILESIZE, PROT_READ | PROT_WRITE , MAP_SHARED, fd, 0); 78 if (addr == MAP_FAILED) 79 { 80 perror("Mmap failed"); 81 return 1; 82 } 83 84 status = msync(addr,FILESIZE,MS_INVALIDATE | MS_SYNC); 85 if (status != 0) 86 { 87 perror("Msync failed"); 88 return 1; 89 } 90 91 munmap(addr,FILESIZE); 92 93 *fdp = fd; 94 return 0; 95 } 96 97 98 /* mmap a 2 page buffer - first page is from fd1, second page from fd2 */ 99 int mapBuffer(char** bufferp,int fd1,int fd2) 100 { 101 void* addr; 102 char *buffer; 103 104 addr = mmap(NULL,pagesize*2, PROT_READ | PROT_WRITE , MAP_SHARED, fd1, 0); 105 if (addr == MAP_FAILED) 106 { 107 perror("Mmap failed"); 108 return 1; 109 } 110 111 buffer = addr; 112 addr = mmap(buffer + pagesize,pagesize, PROT_READ | PROT_WRITE , MAP_FIXED | 113 MAP_SHARED, fd2, 0); 114 115 if (addr == MAP_FAILED) 116 { 117 perror("Mmap2 failed"); 118 return 1; 119 } 120 *bufferp = buffer; 121 return 0; 122 } 123 124 125 int startIO(int fd,char *buffer) 126 { 127 ssize_t len; 128 len = write(fd,buffer,2*pagesize); 129 if (len == -1) 130 { 131 perror("write failed"); 132 return 1; 133 } 134 return 0; 135 } 136 137 138 int main(int argc __unused, char *argv[] __unused) 139 { 140 141 int fdA,fdB,fdDelayA,fdDelayB; 142 int status; 143 char *bufferA,*bufferB; 144 pid_t pid; 145 146 pagesize = getpagesize(); 147 148 if ((prepareFile("A",&fdA)) 149 || (prepareFile("B",&fdB)) 150 || (prepareFile("DelayA",&fdDelayA)) 151 || (prepareFile("DelayB",&fdDelayB)) 152 || (mapBuffer(&bufferA,fdDelayA,fdB)) 153 || (mapBuffer(&bufferB,fdDelayB,fdA))) 154 exit(1); 155 156 pid = fork(); 157 158 if (pid == 0) 159 { 160 status = startIO(fdA,bufferA); 161 exit(status); 162 } 163 164 if (pid == -1) 165 { 166 exit(1); 167 } 168 status = startIO(fdB,bufferB); 169 exit(status); 170 171 } 172 173 174 175 176 177