diff options
Diffstat (limited to 'miscutils')
| -rw-r--r-- | miscutils/Config.in | 16 | ||||
| -rw-r--r-- | miscutils/Makefile.in | 1 | ||||
| -rw-r--r-- | miscutils/readahead.c | 36 |
3 files changed, 53 insertions, 0 deletions
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; +} |