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Michael Opdenacker contributed a readahead applet.

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This commit is contained in:
Rob Landley 2006-08-20 22:12:18 +00:00
parent 289e86a0a5
commit 0e4690d4ef
5 changed files with 60 additions and 0 deletions
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1
include/applets.h
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@ -219,6 +219,7 @@ USE_PRINTF(APPLET(printf, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
USE_PS(APPLET(ps, _BB_DIR_BIN, _BB_SUID_NEVER))
USE_PWD(APPLET(pwd, _BB_DIR_BIN, _BB_SUID_NEVER))
USE_RDATE(APPLET(rdate, _BB_DIR_USR_SBIN, _BB_SUID_NEVER))
USE_READAHEAD(APPLET(readahead, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
USE_READLINK(APPLET(readlink, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
USE_READPROFILE(APPLET(readprofile, _BB_DIR_USR_SBIN, _BB_SUID_NEVER))
USE_REALPATH(APPLET(realpath, _BB_DIR_USR_BIN, _BB_SUID_NEVER))

6
include/usage.h
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@ -2385,6 +2385,12 @@ USE_FEATURE_MDEV_CONFIG( \
"\t-s\tSet the system date and time (default)\n" \
"\t-p\tPrint the date and time"
#define readahead_trivial_usage \
"[FILE]..."
#define readahead_full_usage \
"Preloads FILE(s) in RAM cache so that subsequent reads for those" \
"files do not block on disk I/O."
#ifdef CONFIG_FEATURE_READLINK_FOLLOW
#define USAGE_READLINK_FOLLOW(a) a
#else

16
miscutils/Config.in
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@ -276,6 +276,22 @@ config CONFIG_MT
to advance or rewind a tape past a specified number of archive
files on the tape.
config CONFIG_READAHEAD
bool "readahead"
default n
help
Preload the files listed on the command line into RAM cache so that
subsequent reads on these files will not block on disk I/O.
This applet just calls the readahead(2) system call on each file.
It is mainly useful in system startup scripts to preload files
or executables before they are used. When used at the right time
(in particular when a CPU boundprocess is running) it can
significantly speed up system startup.
As readahead(2) blocks until each file has been read, it is best to
run this applet as a background job.
config CONFIG_RUNLEVEL
bool "runlevel"
default n

1
miscutils/Makefile.in
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@ -24,6 +24,7 @@ MISCUTILS-${CONFIG_LESS} += less.o
MISCUTILS-$(CONFIG_MAKEDEVS) += makedevs.o
MISCUTILS-$(CONFIG_MOUNTPOINT) += mountpoint.o
MISCUTILS-$(CONFIG_MT) += mt.o
MISCUTILS-$(CONFIG_READAHEAD) += readahead.o
MISCUTILS-$(CONFIG_RUNLEVEL) += runlevel.o
MISCUTILS-$(CONFIG_RX) += rx.o
MISCUTILS-$(CONFIG_SETSID) += setsid.o

36
miscutils/readahead.c Normal file
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@ -0,0 +1,36 @@
/* 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 tarball for details.
*/
#include "busybox.h"
int readahead_main(int argc, char **argv)
{
FILE *f;
struct stat stat_buf;
int retval = EXIT_SUCCESS;
if (argc == 1) bb_show_usage();
while (*++argv) {
if ((f = bb_wfopen(*argv, "r")) != NULL) {
int r, fd=fileno(f);
xstat(*argv, &stat_buf);
r = readahead(fd, 0, fdlength(fd));
fclose(f);
if (r >= 0) continue;
}
retval = EXIT_FAILURE;
}
return retval;
}