[ovs-discuss] ovs-vswitchd process huge memory consumption

Wed Mar 6 15:01:13 UTC 2019

I'm thinking if this can be malloc() not returning memory to the system
after peak loads:
*"Occasionally, free can actually return memory to the operating system and
make the process smaller. Usually, all it can do is allow a later call to
malloc to reuse the space. In the meantime, the space remains in your
program as part of a free-list used internally by malloc." [1]*

Does it sound sane? If yes, what would be a best way to check that?

[1] http://www.gnu.org/software/libc/manual/pdf/libc.pdf

Thanks,
Oleg

On Wed, Mar 6, 2019 at 12:34 PM Oleg Bondarev <obondarev at mirantis.com>
wrote:

> Hi,
>
> On Wed, Mar 6, 2019 at 1:08 AM Ben Pfaff <blp at ovn.org> wrote:
>
>> Starting from 0x30, this looks like a "minimatch" data structure, which
>> is a kind of compressed bitwise match against a flow.
>>
>> 00000030: 0000 0000 0000 4014 0000 0000 0000 0000
>> 00000040: 0000 0000 0000 0000 fa16 3e2b c5d5 0000 0000 0022 0000 0000
>>
>> 00000058: 0000 0000 0000 4014 0000 0000 0000 0000
>> 00000068: 0000 0000 ffff ffff ffff ffff ffff 0000 0000 0fff 0000 0000
>>
>> I think this corresponds to a flow of this form:
>>
>>
>> pkt_mark=0xc5d5/0xffff,skb_priority=0x3e2bfa16,reg13=0,mpls_label=2,mpls_tc=1,mpls_ttl=0,mpls_bos=0
>>
>> Is that at all meaningful?  Does it match anything that appears in the
>> OpenFlow flow table?
>>
>
> Not sure, actually fa:16:3e:2b:c5:d5 is a mac address of a neutron port
> (this is an OpenStack cluster) - the port is a VM port.
> fa:16:3e/fa:16:3f - are standard neutron mac prefixes. That makes me think
> those might be some actual eth packets (broadcasts?) that somehow
> stuck in memory..
> So I didn't find anything similar in the flow tables. I'm attaching flows
> of all 5 OVS bridges on the node.
>
>
>>
>> Are you using the kernel or DPDK datapath?
>>
>
> It's kernel datapath, no DPDK. Ubuntu with 4.13.0-45  kernel.
>
>
>>
>> On Tue, Mar 05, 2019 at 08:42:14PM +0400, Oleg Bondarev wrote:
>> > Hi,
>> >
>> > thanks for your help!
>> >
>> > On Tue, Mar 5, 2019 at 7:26 PM Ben Pfaff <blp at ovn.org> wrote:
>> >
>> > > You're talking about the email where you dumped out a repeating
>> sequence
>> > > from some blocks?  That might be the root of the problem, if you can
>> > > provide some more context.  I didn't see from the message where you
>> > > found the sequence (was it just at the beginning of each of the 4 MB
>> > > blocks you reported separately, or somewhere else), how many copies of
>> > > it, or if you were able to figure out how long each of the blocks was.
>> > > If you can provide that information I might be able to learn some
>> > > things.
>> > >
>> >
>> > Yes, those were beginnings of 0x4000000 size blocks reported by the
>> script.
>> > I also checked 0x8000000 blocks reported and the content is the same.
>> > Examples of how those blocks end:
>> >  - https://pastebin.com/D9M6T2BA
>> >  - https://pastebin.com/gNT7XEGn
>> >  - https://pastebin.com/fqy4XDbN
>> >
>> > So basically contents of the blocks are sequences of:
>> >
>> > *00000020: 0000 0000 0000 0000 6500 0000 0000 0000  ........e.......*
>> > *00000030: 0000 0000 0000 4014 0000 0000 0000 0000  ...... at .........*
>> > *00000040: 0000 0000 0000 0000 fa16 3e2b c5d5 0000  ..........>+....*
>> > *00000050: 0000 0022 0000 0000 0000 0000 0000 4014  ...".......... at .*
>> > *00000060: 0000 0000 0000 0000 0000 0000 ffff ffff  ................*
>> > *00000070: ffff ffff ffff 0000 0000 0fff 0000 0000  ................*
>> >
>> > following each other and sometimes separated by sequences like this:
>> >
>> > *00001040: 6861 6e64 6c65 7232 3537 0000 0000 0000  handler257......*
>> >
>> > I ran the scripts against several core dumps of several compute nodes
>> with
>> > the issue and
>> > the picture is pretty much the same: 0x4000000 blocks and less 0x8000000
>> > blocks.
>> > I checked the core dump from a compute node where OVS memory consumption
>> > was ok:
>> > no such block sizes reported.
>> >
>> >
>> > >
>> > > On Tue, Mar 05, 2019 at 09:07:55AM +0400, Oleg Bondarev wrote:
>> > > > Hi Ben,
>> > > >
>> > > > I didn't have a chance to debug the scripts yet, but just in case
>> you
>> > > > missed my last email with examples of repeatable blocks
>> > > > and sequences - do you think we still need to analyze further, will
>> the
>> > > > scripts tell more about the heap?
>> > > >
>> > > > Thanks,
>> > > > Oleg
>> > > >
>> > > > On Thu, Feb 28, 2019 at 10:14 PM Ben Pfaff <blp at ovn.org> wrote:
>> > > >
>> > > > > On Tue, Feb 26, 2019 at 01:41:45PM +0400, Oleg Bondarev wrote:
>> > > > > > Hi,
>> > > > > >
>> > > > > > thanks for the scripts, so here's the output for a 24G core
>> dump:
>> > > > > > https://pastebin.com/hWa3R9Fx
>> > > > > > there's 271 entries of 4MB - does it seem something we should
>> take a
>> > > > > closer
>> > > > > > look at?
>> > > > >
>> > > > > I think that this output really just indicates that the script
>> failed.
>> > > > > It analyzed a lot of regions but didn't output anything useful.
>> If it
>> > > > > had worked properly, it would have told us a lot about data
>> blocks that
>> > > > > had been allocated and freed.
>> > > > >
>> > > > > The next step would have to be to debug the script.  It definitely
>> > > > > worked for me before, because I have fixed at least 3 or 4 bugs
>> based
>> > > on
>> > > > > it, but it also definitely is a quick hack and not something that
>> I can
>> > > > > stand behind.  I'm not sure how to debug it at a distance.  It
>> has a
>> > > > > large comment that describes what it's trying to do.  Maybe that
>> would
>> > > > > help you, if you want to try to debug it yourself.  I guess it's
>> also
>> > > > > possible that glibc has changed its malloc implementation; if so,
>> then
>> > > > > it would probably be necessary to start over and build a new
>> script.
>> > > > >
>> > >
>>
>
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