Re: xenstored memory leak

[Juergen Gross <jgross@suse.com>]

On 06/07/16 15:48, Andrew Cooper wrote:
> On 06/07/16 08:31, Juergen Gross wrote:
>> While testing some patches for support of ballooning in Mini-OS by using
>> the xenstore domain I realized that each xl create/destroy pair would
>> increase memory consumption in Mini-OS by about 5kB. Wondering whether
>> this is a xenstore domain only effect I did the same test with xenstored
>> and oxenstored daemons.
>>
>> xenstored showed the same behavior, the "referenced" size showed by the
>> pmap command grew by about 5kB for each create/destroy pair.
>>
>> oxenstored seemed to be even worse in the beginning (about 6kB for each
>> pair), but after about 100 create/destroys the value seemed to be
>> rather stable.
> 
> Do you mean that after a while, you see oxenstored not leaking any
> further memory, even with new domains being created?

In my test: yes. I did:

while true
do
  xl create minios.xl
  sleep 3
  xl shutdown minios
  sleep 2
done

After about 200 iterations memory usage with oxenstored was stable. I
stopped the loop after more than 1000 iterations.

> Ocaml is a garbage collected languague, so you would expect the process
> to get larger until the GC decides to kick in.

Okay. This explains the pattern.

>> Did anyone notice this memory leak before?
> 
> We have not encountered this in XenServer stress scenarios.

You are using oxenstored, right? The real leak is in xenstored only.

> (It is entirely possible that this specific to something xl does which
> Xapi doesn't.)

I doubt that. I'm seeing the leak with the C-variant of xenstore, both
as daemon and as stubdom.


Juergen


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