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authorRob Landley <rob@landley.net>2006-08-20 22:12:18 +0000
committerRob Landley <rob@landley.net>2006-08-20 22:12:18 +0000
commit0e4690d4ef9fe55ccf6db371c826112809e162f9 (patch)
tree1eac13023c328f3956a00f3e741eb1cda45696d0
parent289e86a0a5b2482fc1b6a442d3acd749639e4d64 (diff)
downloadbusybox-0e4690d4ef9fe55ccf6db371c826112809e162f9.tar.gz
Michael Opdenacker contributed a readahead applet.
-rw-r--r--include/applets.h1
-rw-r--r--include/usage.h6
-rw-r--r--miscutils/Config.in16
-rw-r--r--miscutils/Makefile.in1
-rw-r--r--miscutils/readahead.c36
5 files changed, 60 insertions, 0 deletions
diff --git a/include/applets.h b/include/applets.h
index a8b480b80..0bb257b6d 100644
--- a/include/applets.h
+++ b/include/applets.h
@@ -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))
diff --git a/include/usage.h b/include/usage.h
index 5bc82dc22..ced9f68c7 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -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
diff --git a/miscutils/Config.in b/miscutils/Config.in
index 4296b54ea..9ad342151 100644
--- a/miscutils/Config.in
+++ b/miscutils/Config.in
@@ -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
diff --git a/miscutils/Makefile.in b/miscutils/Makefile.in
index a0b6b7233..25143c10b 100644
--- a/miscutils/Makefile.in
+++ b/miscutils/Makefile.in
@@ -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
diff --git a/miscutils/readahead.c b/miscutils/readahead.c
new file mode 100644
index 000000000..9f1bb47be
--- /dev/null
+++ b/miscutils/readahead.c
@@ -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;
+}