Michael Opdenacker contributed a readahead applet.

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;
+}