From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: A clocksource question Date: Fri, 12 Mar 2010 14:02:38 -0800 Message-ID: <4B9AB9FE.8070601@goop.org> References: <4B962748.90609@invisiblethingslab.com> <4B9A8FDE.8070506@invisiblethingslab.com> <4B9AB126.1070406@goop.org> <201003122256.02254.tobias.geiger@vido.info> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <201003122256.02254.tobias.geiger@vido.info> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Tobias Geiger Cc: xen-devel@lists.xensource.com, Joanna Rutkowska List-Id: xen-devel@lists.xenproject.org On 03/12/2010 01:56 PM, Tobias Geiger wrote: > kbpc2:~# cat > /sys/devices/system/clocksource/clocksource0/current_clocksource > xen > kbpc2:~# cat > /sys/devices/system/clocksource/clocksource0/available_clocksource > xen > kbpc2:~# echo "jiffies" > >> /sys/devices/system/clocksource/clocksource0/current_clocksource >> > kbpc2:~# dmesg | tail -1 > [ 7898.642404] Override clocksource jiffies is not HRT compatible. Cannot switch > while in HRT/NOHZ mode > kbpc2:~# > > Seems like it's not possible to switch to jiffies - however: > kbpc2:~# zcat /proc/config.gz | grep NO_HZ > # CONFIG_NO_HZ is not set > > but CONFIG_SCHED_HRTICK=y > Interesting. BTW, does NO_HZ change the behaviour of this? In principle NO_HZ should be preferable, and particularly in a virtual machine since it should limit the number of timer interrupts. Joanna, are you using NO_HZ? Thanks, J