Hi,
On 8/7/24 15:37, Stefan Hajnoczi wrote:
> On Sat, Aug 03, 2024 at 11:23:21AM +0200, Claudio Fontana wrote:
>> Hello Stefan,
>>
>> did not know where to report this, but the man page mentions you specifically so here I am.
>
> Hi Claudio,
> I wrote the man page for kvm_stat(1) but am not the maintainer of the
> tool. I have CCed the KVM mailing list although it's possible that no
> one actively maintains the tool :).
>
>>
>>
>> There seems to be an issue when kvm_stat is run with:
>>
>> kvm_stat -p xxx -d -t -s yy -c -L FILENAME.csv &
>>
>> specifically due to the ampersand (&), thus running in the background.
>>
>>
>> It seems that kvm_stat gets the interrupt signal (SIGINT), and does write as a result the output to disk,
>> but then instead of terminating, it just hangs there forever.
>
> That is strange. The only signal handler installed by kvm_stat is for
> SIGHUP, so Python should perform the default behavior for SIGINT and
> terminate. I'm not sure why the process would hang.
>
>>
>> So to avoid ending up with a large number of kvm_stat processes lingering on the system,
>> we needed to put a random sleep, and then send a SIGTERM to terminate the kvm_stat processes.
>>
>> Just sending a SIGTERM (without the SIGINT) does terminate the kvm_stat processes, but NO DATA is written to disk (the files show as 0 size).
>
> That makes sense since kvm_stat does not handle SIGTERM. The default
> SIGTERM behavior is to terminal and any output in Python's I/O buffers
> may not have been written to the file.
>
> Maybe kvm_stat should catch SIGINT and SIGTERM. That would give it a
> chance to write out the log before terminating. Do you want to try
> implementing that?I
I think SIGINT would be enough, sure I can give it a try,
Thanks,
C
>
>>
>> This is the workaround script that we currently have:
>>
>> ----
>>
>> #! /bin/bash
>>
>> VM_PIDS=`pgrep qemu-system-`
>>
>> for VM_PID in ${VM_PIDS} ; do
>> # warning: kvm_stat is very fragile, change with care
>> kvm_stat -p ${VM_PID} -d -t -s 1 -c -L kvm_stat_${VM_PID}.csv &
>> done
>>
>> if test "x${VM_PID}" != "x" ; then
>> echo "launched kvm_stat processes, capturing 10 seconds..."
>> sleep 10
>> echo "signaling all kvm_stat processes to write to disk..."
>> pkill -INT -P $$
>> sleep 5
>> sync
>> echo "signaling all kvm_stat processes to die..."
>> pkill -TERM -P $$
>> echo "waiting for kvm_stat processes to exit..."
>> while pgrep -P $$ > /dev/null; do
>> sleep 2
>> echo "still waiting for kvm_stat processes to exit..."
>> done
>> fi
>>
>> echo "Done."
>>
>> ----
>>
>> Feel free to forward to the appropriate mailing list if needed,
>>
>> thanks!
>>
>> Claudio
>>
>> --
>> Claudio Fontana
>> Engineering Manager Virtualization, SUSE Labs Core
>>
>> SUSE Software Solutions Italy Srl
>>
