From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [Xen-devel] Re: About profiling xen Date: Wed, 30 Sep 2009 16:23:53 -0700 Message-ID: <4AC3E889.6060407@goop.org> References: <196324.1267.qm@web94604.mail.in2.yahoo.com> <20090930063747.GG1434@reaktio.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-users-bounces@lists.xensource.com Errors-To: xen-users-bounces@lists.xensource.com To: Marco Tizzoni Cc: "Fajar A." , Fasiha Ashraf , xen , xen-users@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On 09/30/09 02:06, Marco Tizzoni wrote: > Enabling debug on kernel I realized the problem is related to timer accuracy. > ------------------------------------------------------------------------ > hal9k-dom0 ~ # cat /proc/timer_list > Timer List Version: v0.3 > HRTIMER_MAX_CLOCK_BASES: 2 > now at 784689453083 nsecs > > cpu: 0 > clock 0: > .index: 0 > .resolution: 999848 nsecs > [........] > hal9k-dom0 ~ # cat > /sys/devices/system/clocksource/clocksource0/available_clocksource > xen jiffies > hal9k-dom0 ~ # cat > /sys/devices/system/clocksource/clocksource0/current_clocksource > xen > ------------------------------------------------------------------------ > > Is there a way to make available a better timer (hpet,acpi....)? > Your clocksource is "xen", which is the best possible for a PV xen guest. However, a clocksource is for measuring elapsed time, not triggering timers. Unfortunately there doesn't seem to be a /sys file to show the current clockevent source in use, but if you have "xen" clocksource it's almost certainly the xen clockevent. However, this is only relevent if you have CONFIG_NO_HZ and CONFIG_HIGHRES_TIMERS enabled. If you don't then all timers will be quantized to HZ (and your guests will burn lots CPU being needlessly interrupted at HZ). J