Re: Memory leak when adding/removing vhost_user ports

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Wed, Apr 20, 2016 at 08:18:49AM +0200, Christian Ehrhardt wrote:
> On Wed, Apr 20, 2016 at 7:04 AM, Yuanhan Liu <yuanhan.liu@linux.intel.com>
> wrote:
> 
>     On Tue, Apr 19, 2016 at 06:33:50PM +0200, Christian Ehrhardt wrote:
> 
> [...] 
> 
>     > With that applied one (and only one) of my two guests looses connectivity
>     after
>     > removing the ports the first time.
> 
>     Yeah, that's should be because I invoked the "->destroy_device()"
>     callback.
> 
> 
> Shouldn't that not only destroy the particular vhost_user device I remove?

I assume the "not" is typed wrong here, then yes. Well, it turned
out that I accidentally destroyed the first guest (with id 0) with
following code:

	ctx.fh = g_vhost_server.server[i]->fh;
	vhost_destroy_device(ctx);

server[i]->fh is initialized with 0 when no connection is established
(check below for more info), and the first id is started with 0. Anyway,
this could be fixed easily.

> See below for some better details on the test to clarify that.
> 
> 
>     BTW, I'm curious how do you do the test? I saw you added 256 ports, but
>     with 2 guests only? So, 254 of them are idle, just for testing the
>     memory leak bug?
> 
> 
> Maybe I should describe it better:
> 1. Spawn some vhost-user ports (40 in my case)
> 2. Spawn a pair of guests that connect via four of those ports per guest
> 3. Guests only intialize one of that vhost_user based NICs
> 4. check connectivity between guests via the vhost_user based connection
> (working at this stage)
> LOOP 5-7:
>    5. add ports 41-512
>    6. remove  ports 41-512
>    7. check connectivity between guests via the vhost_user based connection

Yes, it's much clearer now. Thanks.

I then don't see it's a leak from DPDK vhost-user, at least not the leak
on "struct virtio_net" I have mentioned before. "struct virito_net" will
not even be allocated for those ports never used (ports 41-512 in your case),
as it will be allocated only when there is a connection established, aka,
a guest is connected.

BTW, will you be able to reproduce it without any connections? Say, all
512 ports are added, and then deleted.

Thanks.

	--yliu

> 
> So the vhost_user ports the guests are using are never deleted.
> Only some extra (not even used) ports are added&removed in the loop to search
> for potential leaks over a longer lifetime of an openvswitch-dpdk based
> solution.
>