[ovs-dev] ovn-northd-ddlog scale issues

Dumitru Ceara dceara at redhat.com
Wed Mar 24 15:03:07 UTC 2021


Hi Ben,

We discussed a bit about this during one of the recent IRC OVN meetings,
but I didn't get around to properly reporting this until now.

I've tried running ovn-northd-ddlog against some large OVN NB/DB
databases extracted from one of our scale testing runs:

http://people.redhat.com/~dceara/ovn-northd-ddlog-tests/20210324/existing-nb-sb/

It seems that ovn-northd-ddlog gets stuck in a busy loop and uses a lot
of memory:

775734 root      10 -10   81.6g  80.8g  22396 S  99.7  64.2   3:50.79 ovn-northd-ddlog

ovn-northd-ddlog is stuck in an (infinite?) loop in
ddlog_transaction_commit_dump_changes():

(gdb) bt
#0  0x00007f2762167e92 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x0000000000891eb3 in std::thread::park ()
#2  0x0000000000530963 in crossbeam_channel::context::Context::wait_until ()
#3  0x0000000000530aa1 in crossbeam_channel::context::Context::with::{{closure}} ()
#4  0x0000000000531f5c in crossbeam_channel::flavors::list::Channel<T>::recv ()
#5  0x000000000075b35d in crossbeam_channel::channel::Receiver<T>::recv ()
#6  0x0000000000512156 in differential_datalog::program::RunningProgram::flush ()
#7  0x000000000050de67 in differential_datalog::program::RunningProgram::transaction_commit ()
#8  0x000000000093f17d in <ovn_northd_ddlog::api::HDDlog as differential_datalog::ddlog::DDlog>::transaction_commit_dump_changes ()
#9  0x000000000040cc40 in ddlog_transaction_commit_dump_changes ()
#10 0x000000000040a758 in ddlog_commit (ddlog=<optimized out>) at northd/ovn-northd-ddlog.c:435
#11 northd_parse_update (update=0x3dc0598, ctx=0x3d71880) at northd/ovn-northd-ddlog.c:435
#12 northd_run (ctx=0x3d71880) at northd/ovn-northd-ddlog.c:512
#13 0x0000000000408edd in main (argc=<optimized out>, argv=<optimized out>) at northd/ovn-northd-ddlog.c:1203

For comparison, running the C version of ovn-northd I get:

2021-03-24T14:48:06.556Z|00033|timeval|WARN|Unreasonably long 11290ms poll interval (10916ms user, 334ms system)
2021-03-24T14:48:14.678Z|00050|timeval|WARN|Unreasonably long 8122ms poll interval (8046ms user, 48ms system)

But after the northd iteration ends, memory usage is OK:

777567 root      10 -10 1657308   1.6g   3496 S   0.0   1.2   0:49.08 ovn-northd

The behavior above is consistent both with current OVN master and also
when cherry-picking the ddlog-related patches that are pending in
patchwork:
http://patchwork.ozlabs.org/project/ovn/list/?series=233075
http://patchwork.ozlabs.org/project/ovn/list/?series=232480
http://patchwork.ozlabs.org/project/ovn/list/?series=233079
http://patchwork.ozlabs.org/project/ovn/list/?series=233080

I didn't try out the changes from the following series though as I
understand they need a v2:
http://patchwork.ozlabs.org/project/ovn/list/?series=232040

Regards,
Dumitru



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