68 lines
1.9 KiB
C
68 lines
1.9 KiB
C
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/* vi: set sw=4 ts=4: */
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/*
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* readahead implementation for busybox
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*
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* Preloads the given files in RAM, to reduce access time.
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* Does this by calling the readahead(2) system call.
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*
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* Copyright (C) 2006 Michael Opdenacker <michael@free-electrons.com>
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*
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* Licensed under GPLv2 or later, see file LICENSE in this source tree.
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*/
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//config:config READAHEAD
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//config: bool "readahead (1.7 kb)"
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//config: default y
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//config: depends on LFS
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//config: help
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//config: Preload the files listed on the command line into RAM cache so that
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//config: subsequent reads on these files will not block on disk I/O.
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//config:
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//config: This applet just calls the readahead(2) system call on each file.
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//config: It is mainly useful in system startup scripts to preload files
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//config: or executables before they are used. When used at the right time
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//config: (in particular when a CPU bound process is running) it can
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//config: significantly speed up system startup.
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//config:
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//config: As readahead(2) blocks until each file has been read, it is best to
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//config: run this applet as a background job.
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//applet:IF_READAHEAD(APPLET(readahead, BB_DIR_USR_SBIN, BB_SUID_DROP))
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//kbuild:lib-$(CONFIG_READAHEAD) += readahead.o
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//usage:#define readahead_trivial_usage
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//usage: "[FILE]..."
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//usage:#define readahead_full_usage "\n\n"
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//usage: "Preload FILEs to RAM"
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#include "libbb.h"
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int readahead_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int readahead_main(int argc UNUSED_PARAM, char **argv)
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{
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int retval = EXIT_SUCCESS;
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if (!argv[1]) {
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bb_show_usage();
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}
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while (*++argv) {
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int fd = open_or_warn(*argv, O_RDONLY);
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if (fd >= 0) {
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off_t len;
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int r;
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/* fdlength was reported to be unreliable - use seek */
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len = xlseek(fd, 0, SEEK_END);
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xlseek(fd, 0, SEEK_SET);
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r = readahead(fd, 0, len);
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close(fd);
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if (r >= 0)
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continue;
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}
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retval = EXIT_FAILURE;
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}
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return retval;
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}
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