65 lines
1.8 KiB
C
65 lines
1.8 KiB
C
/* vi: set sw=4 ts=4: */
|
|
/*
|
|
* readahead implementation for busybox
|
|
*
|
|
* Preloads the given files in RAM, to reduce access time.
|
|
* Does this by calling the readahead(2) system call.
|
|
*
|
|
* Copyright (C) 2006 Michael Opdenacker <michael@free-electrons.com>
|
|
*
|
|
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
|
|
*/
|
|
//config:config READAHEAD
|
|
//config: bool "readahead"
|
|
//config: default y
|
|
//config: depends on LFS
|
|
//config: select PLATFORM_LINUX
|
|
//config: help
|
|
//config: Preload the files listed on the command line into RAM cache so that
|
|
//config: subsequent reads on these files will not block on disk I/O.
|
|
//config:
|
|
//config: This applet just calls the readahead(2) system call on each file.
|
|
//config: It is mainly useful in system startup scripts to preload files
|
|
//config: or executables before they are used. When used at the right time
|
|
//config: (in particular when a CPU bound process is running) it can
|
|
//config: significantly speed up system startup.
|
|
//config:
|
|
//config: As readahead(2) blocks until each file has been read, it is best to
|
|
//config: run this applet as a background job.
|
|
|
|
//usage:#define readahead_trivial_usage
|
|
//usage: "[FILE]..."
|
|
//usage:#define readahead_full_usage "\n\n"
|
|
//usage: "Preload FILEs to RAM"
|
|
|
|
#include "libbb.h"
|
|
|
|
int readahead_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
|
|
int readahead_main(int argc UNUSED_PARAM, char **argv)
|
|
{
|
|
int retval = EXIT_SUCCESS;
|
|
|
|
if (!argv[1]) {
|
|
bb_show_usage();
|
|
}
|
|
|
|
while (*++argv) {
|
|
int fd = open_or_warn(*argv, O_RDONLY);
|
|
if (fd >= 0) {
|
|
off_t len;
|
|
int r;
|
|
|
|
/* fdlength was reported to be unreliable - use seek */
|
|
len = xlseek(fd, 0, SEEK_END);
|
|
xlseek(fd, 0, SEEK_SET);
|
|
r = readahead(fd, 0, len);
|
|
close(fd);
|
|
if (r >= 0)
|
|
continue;
|
|
}
|
|
retval = EXIT_FAILURE;
|
|
}
|
|
|
|
return retval;
|
|
}
|