On 03/08/2018 09:34 AM, David Miller wrote:
From: Stephen Hemminger <stephen@xxxxxxxxxxxxxxxxxx>
Date: Tue, 6 Mar 2018 15:59:20 -0800
Actually dev_load by ethernet name is really a legacy thing that
should just die,
It was kept around so that some very tunnel configuration using special names.
# ifconfig sit0
which probably several web pages still tell users to do...
We have much better control now with ip commands so that this is just
baggage.
As you say, some people use this stuff, so we really can't break
it at this point.
Another problematic legacy behavior is the automatic creation of
fallback tunnels, which hurts netns creation/deletion.
Some environments want to create a netns for every job/task, and they do
not care if the init netns has these tunnels or not.
We have a local patch adding yet another knob to control this, since it
saves a lot of cpu cycles (about 10ms per netns create/delete pair here)
lpk43:~# echo 0 >/proc/sys/net/core/fb_tunnels_only_for_init_net
lpk43:~# time for i in {1..1000}; do unshare -n /bin/false;done
real 0m14.939s
user 0m0.152s
sys 0m1.496s
lpk43:~# unshare -n
lpk43:~# ip link
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN mode DEFAULT group
default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: tunl0@NONE: <NOARP> mtu 1480 qdisc noop state DOWN mode DEFAULT group
default qlen 1000
link/ipip 0.0.0.0 brd 0.0.0.0
3: gre0@NONE: <NOARP> mtu 1476 qdisc noop state DOWN mode DEFAULT group
default qlen 1000
link/gre 0.0.0.0 brd 0.0.0.0
4: gretap0@NONE: <BROADCAST,MULTICAST> mtu 1462 qdisc noop state DOWN
mode DEFAULT group default qlen 1000
link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
5: erspan0@NONE: <BROADCAST,MULTICAST> mtu 1450 qdisc noop state DOWN
mode DEFAULT group default qlen 1000
link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
6: sit0@NONE: <NOARP> mtu 1480 qdisc noop state DOWN mode DEFAULT group
default qlen 1000
link/sit 0.0.0.0 brd 0.0.0.0
7: ip6tnl0@NONE: <NOARP> mtu 1452 qdisc noop state DOWN mode DEFAULT
group default qlen 1000
link/tunnel6 :: brd ::
8: ip6gre0@NONE: <NOARP> mtu 1448 qdisc noop state DOWN mode DEFAULT
group default qlen 1000
link/gre6 00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00 brd
00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00
lpk43:~# exit
logout
lpk43:~# echo 1 >/proc/sys/net/core/fb_tunnels_only_for_init_net
lpk43:~# time for i in {1..1000}; do unshare -n /bin/false;done
real 0m4.169s
user 0m0.202s
sys 0m0.875s
lpk43:~# unshare -n
lpk43:~# ip link
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN mode DEFAULT group
default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
lpk43:~#
