Re: [PATCH v2 net-next 0/7] net: speedup netns create/delete time

On 20/09/2017 2:27 AM, Eric Dumazet wrote:

When rate of netns creation/deletion is high enough,
we observe softlockups in cleanup_net() caused by huge list
of netns and way too many rcu_barrier() calls.

This patch series does some optimizations in kobject,
and add batching to tunnels so that netns dismantles are
less costly.

IPv6 addrlabels also get a per netns list, and tcp_metrics
also benefit from batch flushing.

This gives me one order of magnitude gain.
(~50 ms -> ~5 ms for one netns create/delete pair)

...

Eric Dumazet (7):
   kobject: add kobject_uevent_net_broadcast()
   kobject: copy env blob in one go
   kobject: factorize skb setup in kobject_uevent_net_broadcast()
   ipv6: addrlabel: per netns list
   tcp: batch tcp_net_metrics_exit
   ipv6: speedup ipv6 tunnels dismantle
   ipv4: speedup ipv6 tunnels dismantle

  include/net/ip_tunnels.h |  3 +-
  include/net/netns/ipv6.h |  5 +++
  lib/kobject_uevent.c     | 94 ++++++++++++++++++++++++++----------------------
  net/ipv4/ip_gre.c        | 22 +++++-------
  net/ipv4/ip_tunnel.c     | 12 +++++--
  net/ipv4/ip_vti.c        |  7 ++--
  net/ipv4/ipip.c          |  7 ++--
  net/ipv4/tcp_metrics.c   | 14 +++++---
  net/ipv6/addrlabel.c     | 81 ++++++++++++++++-------------------------
  net/ipv6/ip6_gre.c       |  8 +++--
  net/ipv6/ip6_tunnel.c    | 20 ++++++-----
  net/ipv6/ip6_vti.c       | 23 +++++++-----
  net/ipv6/sit.c           |  9 +++--
  13 files changed, 157 insertions(+), 148 deletions(-)

Hi Eric,

We see a regression introduced in this series, specifically in the 
patches touching lib/kobject_uevent.c.
We tried to figure out what is wrong there, but couldn't point it out.

Bug is that mlx4 driver restart fails, because mlx4_core is still in use.
According to module dependencies, both mlx4_en and mlx4_ib should have 
been unloaded at this point
Please see log below.

This looks to be some kind of a race, as the repro is not deterministic.
Probably the en/ib modules are now mistakenly reloaded.

Any idea what could this be?

Regards,
Tariq


[root@reg-l-vrt-41016-009 ~]# /etc/init.d/openibd stop
Unloading HCA driver:                                      [  OK  ]
[root@reg-l-vrt-41016-009 ~]# /etc/init.d/openibd start
Loading HCA driver and Access Layer:                       [  OK  ]
[root@reg-l-vrt-41016-009 ~]# /etc/init.d/openibd stop
Unloading mlx4_core                                        [FAILED]
rmmod: ERROR: Module mlx4_core is in use