The value you echo to /proc/sys/vm/dirty_writeback_centisecs always get set to one lower than the value you echo, while this is a kernel related bug. bugzilla.kernel.org states: "MAINLINE OR -MM KERNELS ONLY. Please only file bugs against mainline kernels (ie from kernel.org), -mm tree. Distro bugs should not be reported here, but to the distro's own bug tracking system." and since I run gentoo-sources I report it here. Reproducible: Always Steps to Reproduce: 1. echo 6000 > /proc/sys/vm/dirty_writeback_centisecs 2. cat /proc/sys/vm/dirty_writeback_centisecs 3. echo 500 > /proc/sys/vm/dirty_writeback_centisecs 4. cat /proc/sys/vm/dirty_writeback_centisecs Actual Results: # echo 6000 > /proc/sys/vm/dirty_writeback_centisecs # cat /proc/sys/vm/dirty_writeback_centisecs 5999 # echo 500 > /proc/sys/vm/dirty_writeback_centisecs # cat /proc/sys/vm/dirty_writeback_centisecs 499 Expected Results: The value should be the same as I set, and nothing in either kernel source or /usr/src/linux/Documentation indicates that the value will get set to one lower, so it doesn't look like this is intended. I'm not sure if older kernels are also affected, and I don't have the ability to test currently. Also other sysctl's I tested doesn't have this problem. # emerge --info Portage 2.1.3.19 (default-linux/amd64/2007.0/desktop, gcc-4.1.2, glibc-2.6.1-r0, 2.6.24-gentoo x86_64) ================================================================= System uname: 2.6.24-gentoo x86_64 AMD Sempron(tm) Processor 3300+ Timestamp of tree: Mon, 28 Jan 2008 06:46:01 +0000 ccache version 2.4 [disabled] app-shells/bash: 3.2_p17-r1 dev-java/java-config: 1.3.7, 2.0.33-r1 dev-lang/python: 2.4.4-r6 dev-python/pycrypto: 2.0.1-r6 dev-util/ccache: 2.4-r7 sys-apps/baselayout: 1.12.10-r5 sys-apps/sandbox: 1.2.18.1-r2 sys-devel/autoconf: 2.13, 2.61-r1 sys-devel/automake: 1.4_p6, 1.5, 1.6.3, 1.7.9-r1, 1.8.5-r3, 1.9.6-r2, 1.10 sys-devel/binutils: 2.18-r1 sys-devel/gcc-config: 1.4.0-r4 sys-devel/libtool: 1.5.24 virtual/os-headers: 2.6.23-r3 ACCEPT_KEYWORDS="amd64" CBUILD="x86_64-pc-linux-gnu" CFLAGS="-march=k8 -pipe -O2" CHOST="x86_64-pc-linux-gnu" CONFIG_PROTECT="/etc /usr/kde/3.5/env /usr/kde/3.5/share/config /usr/kde/3.5/shutdown /usr/share/X11/xkb /usr/share/config /var/bind /var/gopher/gophermap" CONFIG_PROTECT_MASK="/etc/env.d /etc/env.d/java/ /etc/fonts/fonts.conf /etc/gconf /etc/php/apache2-php5/ext-active/ /etc/php/cgi-php5/ext-active/ /etc/php/cli-php5/ext-active/ /etc/revdep-rebuild /etc/terminfo /etc/udev/rules.d" CXXFLAGS="-march=k8 -pipe -O2" DISTDIR="/usr/portage/distfiles" FEATURES="distlocks metadata-transfer parallel-fetch sandbox sfperms strict suidctl unmerge-orphans userfetch userpriv usersandbox" GENTOO_MIRRORS="http://trumpetti.atm.tut.fi/gentoo/ http://ftp.linux.ee/pub/gentoo/distfiles/ http://mirror.muntinternet.net/pub/gentoo/ http://mirror.gentoo.no/" LINGUAS="en en_GB sv sv_SE" MAKEOPTS="-j1" PKGDIR="/usr/portage/packages" PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --compress --force --whole-file --delete --delete-after --stats --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages --filter=H_**/files/digest-*" PORTAGE_TMPDIR="/var/tmp" PORTDIR="/usr/portage" PORTDIR_OVERLAY="/usr/local/portage/crossdev-overlay /usr/local/portage/cpan-overlay /usr/local/portage/nethack-overlay /usr/local/portage/generic-overlay" SYNC="rsync://rsync.europe.gentoo.org/gentoo-portage" USE="3dnow 3dnowext X acl acpi alsa amd64 arts audiofile bash-completion berkdb bitmap-fonts bzip2 cairo caps ccache cdb cdr cli cracklib crypt cups curl dbus dri dvd dvdr dvdread emacs emboss encode evo exif expat fam fastcgi fbcon firefox flac fontconfig foomaticdb fortran gd gdbm gif glep gmp gnutls gpm gstreamer gtk iconv idea idn ieee1394 imlib iproute2 ipv6 isdnlog javascript joystick jpeg jpeg2k kde kqemu lcms lm_sensors logrotate mad mbox midi mikmod mmx mmxext mng mono mozdevelop mp3 mpeg mudflap mysql mysqli ncurses nls nptl nptlonly nsplugin objc ogg openexr opengl openmp pam pcre pdf perl php physfs pic png ppds pppd python qt3 qt3support qt4 quicktime readline reflection rle scanner sdl session sndfile spell spl sqlite sse sse2 ssl svg tcl tcpd tiff tk truetype truetype-fonts type1-fonts unicode usb utempter vorbis xcomposite xorg xpm xv zlib zsh-completion" ALSA_CARDS="emu10k1 loopback seq-dummy dummy" ALSA_PCM_PLUGINS="adpcm alaw asym copy dmix dshare dsnoop empty extplug file hooks iec958 ioplug ladspa lfloat linear meter mulaw multi null plug rate route share shm softvol" ELIBC="glibc" INPUT_DEVICES="keyboard mouse joystick" KERNEL="linux" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LINGUAS="en en_GB sv sv_SE" USERLAND="GNU" VIDEO_CARDS="ati radeon vesa fbdev r128 nv nvidia" Unset: CPPFLAGS, CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LANG, LC_ALL, LDFLAGS, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS What other information do you want attached? Kernel config? dmesg?
Can you reproduce the error with vanilla-sources-2.6.24 ?
I'm afraid I don't have the time to build a new kernel and test currently, I may be able to test next week or so, at earliest. However I asked in #gentoo-amd64 and a user that did have vanilla-sources-2.6.24-rc8 could reproduce it. (No other users using vanilla-sources were there then).
"Distro bugs should not be reported here, but to the distro's own bug tracking system." If you can reproduce it with vanilla, then it is not a distro dependant bug. :)
This has been reported at http://bugzilla.kernel.org/show_bug.cgi?id=9838 now.
Thanks, will track upstream bug
