On Friday, March 30, 2012 04:56:17 PM Jeshua Lacock did opine: > On Mar 30, 2012, at 1:20 AM, Viesturs Lؤپcis wrote: > >> Does anyone know of some known settings to try disabling in CMOS to > >> possibly get lower numbers? My 1.0ms Max Jitter is under 9300, but > >> if possible I would like to get it even lower. > > > > IMHO it is very good number already. You have max jitter of 9,3 us in > > a 1000 us thread, so the max deviance is less than 1%, LinuxCNC will > > perfectly handle that. > > At the moment I can remember of 2 things to do, if You want to try: > > 1) for Intel processors, hyperthreading might be disabled; > > 2) for multi-core processors, one or more processors can be isolated > > exclusively for real-time tasks with isolcpus parameter; > > > > http://wiki.linuxcnc.org/cgi-bin/wiki.pl?RealTime > > Thanks for your explanation Viesturs! > > And, that is very interesting! When I run the CPU hog, my max jitter > goes down to about 1,000! > > I would like to set the CPU as instructed, but I have never used grub > before. I assume I add "isolcpus=1" to the /boot/grub/grub.cfg file - > but I am not sure where to add it. Any suggestions would be greatly > appreciated, thanks! > > > Best, > > Jeshua Lacock > Founder/Engineer > 3DTOPO Incorporated > <http://3DTOPO.com> > Phone: 208.462.4171
It is better to put it as a file in /etc/grub.d/, named as "07_rtai" as this way it can maybe survive a kernel update. NOTE: My mailers word wrap has been turned off, so should yours to properly read this. The file:+++++ (clip below) +++++ #! /bin/sh -e # grub-mkconfig helper script. # Copyright (C) 2006,2007,2008,2009,2010 Free Software Foundation, Inc. # # GRUB is free software: you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation, either version 3 of the License, or # (at your option) any later version. # # GRUB is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with GRUB. If not, see <http://www.gnu.org/licenses/>. ############################################################################## # this is Kent Reed's attempt to create 07_rtai from 10_linux 2011/04/07 # V0.1 # # produces grub2 boot menu entries for rtai kernels appending "isolcpus=1" # after $GRUB_CMDLINE_LINUX_DEFAULT (whose value is set in /etc/default/grub) # NOTE1: an unmodified 10_linux will later create more grub entries for the # same kernels using only $GRUB_CMDLINE_LINUX_DEFAULT # NOTE2: deep in grub2 is a list of allowable user-defined keys so # I couldn't simply define a new GRUB_CMDLINE_RTAI_DEFAULT # in /etc/default/grub---SIGH! # NOTE3: following this comment block, changes to 10_linux are preceded # by lines beginning #KAR: # NOTE4: since grub scripts aren't true shell scripts, I made no attempt # to break new ground. I just copied and modified existing code # NOTE5: does it make sense to add isolcpus=1 to recovery mode? ############################################################################## prefix=/usr exec_prefix=${prefix} bindir=${exec_prefix}/bin libdir=${exec_prefix}/lib . ${libdir}/grub/grub-mkconfig_lib #KAR: define new local strings for convenience # if you want to change the rtai-kernel boot parameters, here's an easy # place to do it. ISOLCPUS="isolcpus=1" GRUB_CMDLINE_LINUX_RTAI="${GRUB_CMDLINE_LINUX_DEFAULT} ${ISOLCPUS}" export TEXTDOMAIN=grub export TEXTDOMAINDIR=@LOCALEDIR@ CLASS="--class gnu-linux --class gnu --class os" if [ "x${GRUB_DISTRIBUTOR}" = "x" ] ; then OS=GNU/Linux else OS="${GRUB_DISTRIBUTOR}" CLASS="--class $(echo ${GRUB_DISTRIBUTOR} | tr '[A-Z]' '[a-z]' | cut -d' ' -f1) ${CLASS}" fi # loop-AES arranges things so that /dev/loop/X can be our root device, but # the initrds that Linux uses don't like that. case ${GRUB_DEVICE} in /dev/loop/*|/dev/loop[0-9]) GRUB_DEVICE=`losetup ${GRUB_DEVICE} | sed -e "s/^[^(]*(\([^)]\+\)).*/\1/"` # We can't cope with devices loop-mounted from files here. case ${GRUB_DEVICE} in /dev/*) ;; *) exit 0 ;; esac ;; esac if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \ || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \ || [ "`grub-probe -t abstraction --device ${GRUB_DEVICE} | sed -e 's,.*\(lvm\).*,\1,'`" = "lvm" ] ; then LINUX_ROOT_DEVICE=${GRUB_DEVICE} else LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID} fi # add crashkernel option if we have the required tools if [ -x "/usr/bin/makedumpfile" ] && [ -x "/sbin/kexec" ]; then GRUB_CMDLINE_EXTRA="$GRUB_CMDLINE_EXTRA crashkernel=384M-2G:64M,2G-:128M" fi linux_entry () { os="$1" version="$2" recovery="$3" args="$4" if ${recovery} ; then title="$(gettext_quoted "%s, with Linux %s (recovery mode)")" else #KAR: augment title to make sensible grub2 boot menu entry title="$(gettext_quoted "%s, with Linux %s (${ISOLCPUS})")" fi printf "menuentry '${title}' ${CLASS} {\n" "${os}" "${version}" cat << EOF recordfail EOF save_default_entry | sed -e "s/^/\t/" if [ "x$GRUB_GFXPAYLOAD_LINUX" != x ]; then cat << EOF set gfxpayload=$GRUB_GFXPAYLOAD_LINUX EOF fi if [ -z "${prepare_boot_cache}" ]; then prepare_boot_cache="$(prepare_grub_to_access_device ${GRUB_DEVICE_BOOT} | sed -e "s/^/\t/")" fi printf '%s\n' "${prepare_boot_cache}" if [ "x$5" != "xquiet" ]; then cat << EOF echo '$(printf "$(gettext_quoted "Loading Linux %s ...")" ${version})' EOF fi cat << EOF linux ${rel_dirname}/${basename} root=${linux_root_device_thisversion} ro ${args} EOF if [ "x$5" != "xquiet" ]; then cat << EOF echo '$(gettext_quoted "Loading initial ramdisk ...")' EOF fi if test -n "${initrd}" ; then cat << EOF initrd ${rel_dirname}/${initrd} EOF fi cat << EOF } EOF } blacklisted_kernel() { local r="" case "${1}" in *-ec2) r="linux-ec2";; # LP: #671097 esac [ -n "${r}" ] && { echo "Skipping linux image [$r]: ${1}" >&2; return 0; } return 1; } #KAR: add new function to test if kernel name ends in -rtai rtai_kernel() { local r="" case "${1}" in *-rtai) r="true";; esac [ -n "${r}" ] && { return 0; } return 1; } #KAR: add rtai-kernel test in determination of suitable kernels list=`for i in /boot/vmlinu[xz]-* /vmlinu[xz]-* ; do if grub_file_is_not_garbage "$i" && ! blacklisted_kernel "$i" && rtai_kernel "$i" ; then echo -n "$i "; fi done` prepare_boot_cache= while [ "x$list" != "x" ] ; do linux=`version_find_latest $list` #KAR: modify message echo "Found rtai linux image: $linux" >&2 basename=`basename $linux` dirname=`dirname $linux` rel_dirname=`make_system_path_relative_to_its_root $dirname` version=`echo $basename | sed -e "s,^[^0-9]*-,,g"` alt_version=`echo $version | sed -e "s,\.old$,,g"` linux_root_device_thisversion="${LINUX_ROOT_DEVICE}" initrd= for i in "initrd.img-${version}" "initrd-${version}.img" \ "initrd-${version}" "initrd.img-${alt_version}" \ "initrd-${alt_version}.img" "initrd-${alt_version}"; do if test -e "${dirname}/${i}" ; then initrd="$i" break fi done if test -n "${initrd}" ; then #KAR: modify message echo "Found rtai initrd image: ${dirname}/${initrd}" >&2 else # "UUID=" magic is parsed by initrds. Since there's no initrd, it can't work here. linux_root_device_thisversion=${GRUB_DEVICE} fi #KAR: change original production to use GRUB_CMDLINE_LINUX_RTAI instead of GRUB_CMDLINE_LINUX_DEFAULT linux_entry "${OS}" "${version}" false \ "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_EXTRA} ${GRUB_CMDLINE_LINUX_RTAI}" \ quiet if [ "x${GRUB_DISABLE_LINUX_RECOVERY}" != "xtrue" ]; then linux_entry "${OS}" "${version}" true \ "single ${GRUB_CMDLINE_LINUX}" fi list=`echo $list | tr ' ' '\n' | grep -vx $linux | tr '\n' ' '` done ==============clip above & fix mailer damages if any======== I _think_ this is in the wiki someplace too. Many thanks to Kent Reed for this bit of magic. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> The rule on staying alive as a forecaster is to give 'em a number or give 'em a date, but never give 'em both at once. -- Jane Bryant Quinn ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
