Date: Tue, 19 Oct 2010 08:07:54 +0200 From: David Naylor <naylor.b.david@gmail.com> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: freebsd-current@freebsd.org Subject: Re: geom_sched usage Message-ID: <201010190807.59491.naylor.b.david@gmail.com> In-Reply-To: <20101018195125.GA46115@onelab2.iet.unipi.it> References: <201010180943.37042.naylor.b.david@gmail.com> <20101018195125.GA46115@onelab2.iet.unipi.it>
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On Monday 18 October 2010 21:51:25 Luigi Rizzo wrote:
> On Mon, Oct 18, 2010 at 09:43:28AM +0200, David Naylor wrote:
> > Hi,
> >=20
> > I've used geom_sched to some success. Normally I do not notice anything
> > but today I was copying big files over a gigabit ethernet and my laptop
> > was not very responsive. I loaded gsched and the responsiveness
> > improved (although still rather bad for anything requiring something
> > from the HDD).
> >=20
> > Thank you for all this work :-)
> >=20
> > Some questions I have:
> > - with a gmirror should the gsched be attached to the underlying devic=
es
> > (aka
> >=20
> > /dev/ad?) or to the mirror device (aka /dev/mirror/?)?
>=20
> always attach as close as possible to the hardware.
Thanks. =20
> > - is there anyway to automatically attach gsched to a device on startup
> > (i.e.
> >=20
> > in rc.conf)?
>=20
> no, you have to build some script yourself.
Would there be any interest in having a rc.d/ script? I would find it=20
conveniant to specify a single rc.conf line and get scheduling for all my=20
devices. PC-BSD might find such functionality useful. =20
See attached for my first draft at such a script, I'm willing to hash it in=
to=20
shape. =20
> > - is there a way to prioritise random IO (vs sequential reads from big
> >=20
> > files)?
>=20
> no way to do that, but you can modify the quantum size and time to
> let sequential reads get shorter chunks
>=20
> kern.geom.sched.rr.quantum_kb: 8192
> kern.geom.sched.rr.quantum_ms: 100
> kern.geom.sched.rr.wait_ms: 10
>=20
> e.g. on a laptop it might make sense to set
> quantum_ms=3D50 and quantum_kb=3D2048
Is there a manual page that describes these sysctls? It looks like, in my=
=20
case, scp just hogs resources. =20
I do perceive some improvements in normal usage. Thanks
> > - gsched_as does not appear to be installed.
>=20
> true, gsched_as was just a proof of concept and gsched_rr
> includes anticipation and round robin, so it is a superset of gsched_as
Thanks for clarity.
Regards,
David
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#!/bin/sh
#
# $FreeBSD$
#
# Specify gsched_enable=3D"YES" in /etc/rc.conf(.local) to activate schedul=
ing on
# storage devices. =20
#=20
# gsched_devs is a space separated list of accepted devices. If empty all
# storage devices are used
#
# gsched_$dev specifies the sheduling algorithm to use (e.g. `rr')
# TODO:
# - add gsched profiles, such as `desktop' for kern.geom.sched.rr tunables
# PROVIDE: gsched
# KEYWORD: nojail
=2E /etc/rc.subr
gsched_enable=3D${gsched_enable:-NO}
name=3D"gsched"
rcvar=3D`set_rcvar`
command=3D"/sbin/${name}"
start_cmd=3D"gsched_start"
stop_cmd=3D"gsched_stop"
gsched_start_dev()
{
local _gsched_dev _gsched_profile _gsched_args
_gsched_dev=3D$1
# Check if sched algo was specified
#
eval _gsched_profile=3D\$gsched_${_gsched_dev}
if [ -n "${_gsched_profile}" ]; then
_gsched_args=3D"-a ${_gsched_profile}"
fi
=09
# Start gsched for ${_gsched_dev}
${command} insert ${_gsched_args} ${_gsched_dev}
}
gsched_all_devs()
{
local _dev
# Only supports upto 100 devices per device class
# XXX: what other storage devices are there?
for _dev in `cd /dev; echo *`; do
case ${_dev} in
ad[0-9]|ad[0-9][0-9])
echo ${_dev}
;;
ada[0-9]|ada[0-9][0-9])
echo ${_dev}
;;
da[0-9]|da[0-9][0-9])
echo ${_dev}
;;
esac
done
}
gsched_start()
{
local _gsched_devs _g _gsched_devs_recon
_gsched_devs=3D$*
if [ -z "${_gsched_devs}" ]; then
# Use devices specified by gsched_devs
_gsched_devs=3D${gsched_devs}
# If no devices are specified then use all we can find
if [ -z "${_gsched_devs}" ]; then
_gsched_devs=3D`gsched_all_devs`
fi
elif [ -n "${gsched_devs}" ]; then
# Make sure the custom device is one of the accepted
for _g in ${_gsched_devs}; do
case ${gsched_devs} in
# _g is either by itself, at the start, middle
# or the end of gsched_devs
${_g}|${_g}\ *|*\ ${_g}\ *|*\ ${_g})
_gsched_devs_recon=3D"${_gsched_devs_recon} ${_g}"
;;
esac
done
_gsched_devs=3D${_gsched_devs_recon}
fi
echo -n "Starting gsched devices:"
for _g in ${_gsched_devs}; do
echo -n " $_g"
gsched_start_dev $_g
done
echo "."
}
gsched_stop_dev() {
local _gsched_dev
_gsched_dev=3D$1
${command} destroy ${_gsched_dev}.sched.
}
gsched_stop() {
local _gsched_devs _g
_gsched_devs=3D$*
if [ -z "${_gsched_devs}" ]; then
# Use devices specified by gsched_devs
_gsched_devs=3D${gsched_devs}
# If no devices are specified then use all we can find
if [ -z "${_gsched_devs}" ]; then
_gsched_devs=3D`gsched_all_devs`
fi
fi
echo -n "Stopping gsched devices:"
for _g in ${_gsched_devs}; do
echo -n " $_g"
gsched_stop_dev $_g
done
echo "."
}
load_rc_config $name
run_rc_command $*
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