On Sat, Mar 21, 2009 at 03:30:39PM +1030, Kevin Shanahan wrote: > On Thu, 2009-03-19 at 07:54 +1030, Kevin Shanahan wrote: > > On Wed, 2009-03-18 at 11:46 +1030, Kevin Shanahan wrote: > > > On Wed, 2009-03-18 at 01:20 +0100, Frederic Weisbecker wrote: > > > > Ok, I've made a small script based on yours which could do this job. > > > > You will just have to set yourself a threshold of latency > > > > that you consider as buggy. I don't remember the latency you observed. > > > > About 5 secs right? > > > > > > > > It's the "thres" variable in the script. > > > > > > > > The resulting trace should be a mixup of the function graph traces > > > > and scheduler events which look like this: > > > > > > > > gnome-screensav-4691 [000] 6716.774277: 4691:120:S ==> [000] 0:140:R <idle> > > > > xfce4-terminal-4723 [001] 6716.774303: 4723:120:R + [001] 4289:120:S Xorg > > > > xfce4-terminal-4723 [001] 6716.774417: 4723:120:S ==> [001] 4289:120:R Xorg > > > > Xorg-4289 [001] 6716.774427: 4289:120:S ==> [001] 0:140:R <idle> > > > > > > > > + is a wakeup and ==> is a context switch. > > > > > > > > The script will loop trying some pings and will only keep the trace that matches > > > > the latency threshold you defined. > > > > > > > > Tell if the following script work for you. > > > > ... > > > > > Either way, I'll try to get some results in my maintenance window > > > tonight. > > > > Testing did not go so well. I compiled and booted > > 2.6.29-rc8-tip-02630-g93c4989, but had some problems with the system > > load when I tried to start tracing - it shot up to around 16-20 or so. I > > started shutting down VMs to try and get it under control, but before I > > got back to tracing again the machine disappeared off the network - > > unresponsive to ping. > > > > When I got in this morning, there was nothing on the console, nothing in > > the logs to show what went wrong. I will try again, but my next chance > > will probably be Saturday. Stay tuned. > > Okay, new set of traces have been uploaded to: > > http://disenchant.net/tmp/bug-12465/trace-3/ > > These were done on the latest tip, which I pulled down this morning: > 2.6.29-rc8-tip-02744-gd9937cb. > > The system load was very high again when I first tried to trace with > sevarl guests running, so I ended up only having the one guest running > and thankfully the bug was still reproducable that way. > > Fingers crossed this set of traces is able to tell us something. > > Regards, > Kevin. > > Sorry, I've been late to answer. As I explained in my previous mail, you trace is only a snapshot that happened in 10 msec. I experimented different sizes for the ring buffer but even a 1 second trace require 20 Mo of memory. And a so huge trace would be impractical. I think we should keep the trace filters we had previously. If you don't minde, could you please retest against latest -tip the following updated patch? Iadded the filters, fixed the python subshell and also flushed the buffer more nicely according to a recent feature in -tip: echo > trace instead of switching to nop. You will need to pull latest -tip again. Thanks a lot Kevin! #!/bin/bash # Switch off all CPUs except for one to simplify the trace echo 0 > /sys/devices/system/cpu/cpu1/online echo 0 > /sys/devices/system/cpu/cpu2/online echo 0 > /sys/devices/system/cpu/cpu3/online # Make sure debugfs has been mounted if [ ! -d /sys/kernel/debug/tracing ]; then mount -t debugfs debugfs /sys/kernel/debug fi # Set up the trace parameters pushd /sys/kernel/debug/tracing || exit 1 echo 0 > tracing_enabled echo function_graph > current_tracer echo funcgraph-abstime > trace_options echo funcgraph-proc > trace_options # Set here the kvm IP addr addr="hermes-old" # Set here a threshold of latency in sec thres="5000" found="False" lat=0 prefix=/sys/kernel/debug/tracing echo 1 > $prefix/events/sched/sched_wakeup/enable echo 1 > $prefix/events/sched/sched_switch/enable # Set the filter for functions to trace echo '' > set_ftrace_filter # clear filter functions echo '*sched*' >> set_ftrace_filter echo '*wake*' >> set_ftrace_filter echo '*kvm*' >> set_ftrace_filter # Reset the function_graph tracer echo function_graph > $prefix/current_tracer while [ "$found" != "True" ] do # Flush the previous buffer echo trace > $prefix/trace echo 1 > $prefix/tracing_enabled lat=$(ping -c 1 $addr | grep rtt | grep -Eo " [0-9]+.[0-9]+") echo 0 > $prefix/tracing_enabled echo $lat found=$(python -c "print float(str($lat).strip())") sleep 0.01 done echo 0 > $prefix/events/sched/sched_wakeup/enable echo 0 > $prefix/events/sched/sched_switch/enable echo "Found buggy latency: $lat" echo "Please send the trace you will find on $prefix/trace" -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
