functional/threadsappend/threadsappend.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Copyright (c) 2013 by Delphix. All rights reserved.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <thread.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>

/*
 * The size of the output file, "go.out", should be 80*8192*2 = 1310720
 *
 * $ cd /tmp; go; ls -l go.out
 * done.
 * -rwxr-xr-x   1 jdm   staff   1310720 Apr 13 19:45 go.out
 * $ cd /zfs; go; ls -l go.out
 * done.
 * -rwxr-xr-x   1 jdm   staff   663552 Apr 13 19:45 go.out
 *
 * The file on zfs is short as it does not appear that zfs is making the
 * implicit seek to EOF and the actual write atomic. From the SUSv3
 * interface spec, behavior is undefined if concurrent writes are performed
 * from multi-processes to a single file. So I don't know if this is a
 * standards violation, but I cannot find any such disclaimers in our
 * man pages. This issue came up at a customer site in another context, and
 * the suggestion was to open the file with O_APPEND, but that wouldn't
 * help with zfs(see 4977529). Also see bug# 5031301.
 */

static int outfd = 0;

static void *
go(void *data)
{
    int i = 0, n = *(int *)data;
    char buf[8192] = {0};
    (void) memset(buf, n, sizeof (buf));

    for (i = 0; i < 80; i++) {
        (void) write(outfd, buf, sizeof (buf));
    }
    return (NULL);
}

static void
usage()
{
    (void) fprintf(stderr,
        "usage: zfs_threadsappend <file name>\n");
    exit(1);
}

int
main(int argc, char **argv)
{
    int ret = 0;
    long    ncpus = 0;
    int i;

    if (argc != 2) {
        usage();
    }

    ncpus = sysconf(_SC_NPROCESSORS_ONLN);
    if (ncpus < 0) {
        (void) fprintf(stderr,
            "Invalid return from sysconf(_SC_NPROCESSORS_ONLN)"
            " : errno (decimal)=%d\n", errno);
        exit(1);
    }
    if (ncpus < 2) {
        (void) fprintf(stderr,
            "Must execute this binary on a multi-processor system\n");
        exit(1);
    }

    outfd = open(argv[optind++], O_RDWR|O_CREAT|O_APPEND|O_TRUNC, 0777);
    if (outfd == -1) {
        (void) fprintf(stderr,
            "zfs_threadsappend: "
            "open(%s, O_RDWR|O_CREAT|O_APPEND|O_TRUNC, 0777)"
            " failed\n", argv[optind]);
        perror("open");
        exit(1);
    }

    for (i = 0; i < 2; i++) {
        ret = thr_create(NULL, 0, go, (void *)&i, 0, NULL);
        if (ret != 0) {
            (void) fprintf(stderr,
                "zfs_threadsappend: thr_create(#%d) "
                "failed error=%d\n", i+1, ret);
            exit(1);
        }
    }

    while (thr_join(0, NULL, NULL) == 0)
        continue;

    return (0);
}