From: David S. Miller <davem@davemloft.net>
Date: Tue, 19 Sep 2017 23:32:24 +0000 (-0700)
Subject: Merge branch 'net-speedup-netns-create-delete-time'
X-Git-Tag: v4.15-rc1~84^2~689
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=8ca712c373a462cfa1b62272870b6c2c74aa83f9;p=linux.git

Merge branch 'net-speedup-netns-create-delete-time'

Eric Dumazet says:

====================
net: speedup netns create/delete time

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)

Tested:

for i in `seq 1 40`
do
 (for j in `seq 1 100` ; do  unshare -n /bin/true >/dev/null ; done) &
done
wait ; grep net_namespace /proc/slabinfo

Before patch series :

$ time ./add_del_unshare.sh
net_namespace        116    258   5504    1    2 : tunables    8    4    0 : slabdata    116    258      0

real	3m24.910s
user	0m0.747s
sys	0m43.162s

After :
$ time ./add_del_unshare.sh
net_namespace        135    291   5504    1    2 : tunables    8    4    0 : slabdata    135    291      0

real	0m22.117s
user	0m0.728s
sys	0m35.328s
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
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8ca712c373a462cfa1b62272870b6c2c74aa83f9