[erlang-bugs] Scheduler Wall Time Statistics live|dead locking a process.
Wed Jul 18 15:50:08 CEST 2012
Hi there Patrick!
I can't exactly afford to dump core on one of the servers right now
because yeah, it would interrupt the service. I could however set one VM
up on the server that just sits and calls vmstats and does some busy
test work, pushing it to a fake StatsD server to reproduce it; maybe it
I can get going setting stuff up; how should I dump the core for it to
be useful for you?
On 12-07-18 9:44 AM, wrote:
> Hi Fred!
> On Wed, 18 Jul 2012, Fred Hebert wrote:
>> Hi there,
>> If you go on erlang-questions, you'll find the following thread I
>> started regarding one of my gen_servers locking up forever until I
>> try to connect to the VM:
>> And the information following it in
>> The gist of it is that apparently, the gen_server gets stuck while
>> calling erlang:statistics(scheduler_wall_time). A process info dump
>> on it returns:
>> with the interesting parts:
>> I'm unsure what exactly causes the problem, and we're running the VM
>> with default arguments when it comes to scheduling and layout. It
>> happens even when the virtual machine is under relatively low load
>> (scheduler active wall time is less than 5%, but more than 2% of the
>> total wall time when averaging all cores) and can also happen under
>> higher load.
> Ouch... Seems like one of the schedulers does not understand that it
> should report data back to the process. Is there any chance of dumping
> core of a machine where it hangs, or would that mean interruption of
> service? I *really* would like to know what the schedulers are doing
> when they should be reporting back...
>> Only that process appears affected.
> Yes, it's just waiting for a message that does not arrive, one that
> should be sent from the VM when statistics for the scheduler is
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