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Message-ID: <177465a0-aaba-4063-e451-ebbf46728b77@itcare.pl>
Date: Tue, 15 Aug 2017 18:30:12 +0200
From: Paweł Staszewski <pstaszewski@...are.pl>
To: Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: 100% CPU load when generating traffic to destination network that
nexthop is not reachable
Hi
Doing some tests i discovered that when traffic is send by pktgen to
forwarding host where nexthop for destination network on forwarding
router is not reachable i have 100% cpu on all cores and perf top show
mostly:
77.19% [kernel] [k] queued_spin_lock_slowpath
10.20% [kernel] [k] acpi_processor_ffh_cstate_enter
1.41% [kernel] [k] queued_write_lock_slowpath
Configuration of forwarding host below:
ip a
Receiving interface:
8: enp175s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state
UP group default qlen 1000
link/ether 0c:c4:7a:d8:5d:1c brd ff:ff:ff:ff:ff:ff
inet 10.0.0.1/30 scope global enp175s0f0
valid_lft forever preferred_lft forever
inet6 fe80::ec4:7aff:fed8:5d1c/64 scope link
valid_lft forever preferred_lft forever
Transmitting vlans (binded to: enp175s0f1)
12: vlan1000@...175s0f1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
qdisc noqueue state UP group default qlen 1000
link/ether 0c:c4:7a:d8:5d:1d brd ff:ff:ff:ff:ff:ff
inet 10.10.0.1/30 scope global vlan1000
valid_lft forever preferred_lft forever
inet6 fe80::ec4:7aff:fed8:5d1d/64 scope link
valid_lft forever preferred_lft forever
13: vlan1001@...175s0f1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
qdisc noqueue state UP group default qlen 1000
link/ether 0c:c4:7a:d8:5d:1d brd ff:ff:ff:ff:ff:ff
inet 10.10.1.1/30 scope global vlan1001
valid_lft forever preferred_lft forever
inet6 fe80::ec4:7aff:fed8:5d1d/64 scope link
valid_lft forever preferred_lft forever
14: vlan1002@...175s0f1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500
qdisc noqueue state UP group default qlen 1000
link/ether 0c:c4:7a:d8:5d:1d brd ff:ff:ff:ff:ff:ff
inet 10.10.2.1/30 scope global vlan1002
valid_lft forever preferred_lft forever
inet6 fe80::ec4:7aff:fed8:5d1d/64 scope link
valid_lft forever preferred_lft forever
Routing table:
10.0.0.0/30 dev enp175s0f0 proto kernel scope link src 10.0.0.1
10.10.0.0/30 dev vlan1000 proto kernel scope link src 10.10.0.1
10.10.1.0/30 dev vlan1001 proto kernel scope link src 10.10.1.1
10.10.2.0/30 dev vlan1002 proto kernel scope link src 10.10.2.1
172.16.0.0/24 via 10.10.0.2 dev vlan1000
172.16.1.0/24 via 10.10.1.2 dev vlan1001
172.16.2.0/24 via 10.10.2.2 dev vlan1002
pktgen is transmitting packets to this forwarding hosts and generating
random destinations from ip range:
pg_set $dev "dst_min 172.16.0.1"
pg_set $dev "dst_max 172.16.2.255"
So when packets with destination network 172.16.0.0/24 are reaching
forwarding host then are routed via 10.10.0.2 dev vlan1000
for packets with destination network 172.16.1.0/24 forwarding host
routing them via 10.10.1.2 dev vlan1001
and last network 172.16.2.0/24 is routed via 10.10.2.2 dev vlan1002
Normally when situation is like this:
ip neigh ls dev vlan1000
10.10.0.2 lladdr ac:1f:6b:2c:18:89 REACHABLE
ip neigh ls dev vlan1001
10.10.1.2 lladdr ac:1f:6b:2c:18:89 REACHABLE
ip neigh ls dev vlan1002
10.10.2.2 lladdr ac:1f:6b:2c:18:89 REACHABLE
There is no problem router is receiving 11Mpps and forwarding then
equally to vlans:
bwm-ng v0.6.1 (probing every 1.000s), press 'h' for help
input: /proc/net/dev type: rate
- iface Rx Tx Total
==============================================================================
vlan1002: 0.00 P/s 3877006.00 P/s 3877006.00 P/s
vlan1001: 0.00 P/s 3877234.75 P/s 3877234.75 P/s
enp175s0f0: 11962601.00 P/s 0.00 P/s 11962601.00 P/s
vlan1000: 0.00 P/s 3862602.00 P/s 3862602.00 P/s
------------------------------------------------------------------------------
total: 11962601.00 P/s 11616843.00 P/s 23579444.00 P/s
And perf top shows like this:
PerfTop: 210522 irqs/sec kernel:99.7% exact: 0.0% [4000Hz
cycles], (all, 56 CPUs)
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
26.98% [kernel] [k] do_raw_spin_lock
7.69% [kernel] [k] acpi_processor_ffh_cstate_enter
4.92% [kernel] [k] fib_table_lookup
4.28% [mlx5_core] [k] mlx5e_xmit
4.01% [mlx5_core] [k] mlx5e_handle_rx_cqe
2.71% [kernel] [k] virt_to_head_page
2.21% [kernel] [k] tasklet_action
1.87% [mlx5_core] [k] mlx5_eq_int
1.58% [kernel] [k] ipt_do_table
1.55% [mlx5_core] [k] mlx5e_poll_tx_cq
1.53% [kernel] [k] irq_entries_start
1.48% [kernel] [k] __dev_queue_xmit
1.44% [kernel] [k] __build_skb
1.30% [mlx5_core] [k] eq_update_ci
1.20% [kernel] [k] read_tsc
1.10% [kernel] [k] ip_finish_output2
1.06% [kernel] [k] ip_rcv
1.02% [kernel] [k] netif_skb_features
1.01% [mlx5_core] [k] mlx5_cqwq_get_cqe
0.95% [kernel] [k] __netif_receive_skb_core
But when i will disable any vlan on the switch - for example I will do
this for vlan1002
(Forwarding host is connected thru switch where are vlans to the sink host)
root@...ulus:~# ip link set down dev vlan1002.49
root@...ulus:~# ip link set down dev vlan1002.3
root@...ulus:~# ip link set down dev brtest1002
Wait for fdb to expire on switch.
there is incomplete arp on interface vlan1002
ip neigh ls dev vlan1002
10.10.2.2 INCOMPLETE
pktgen is still pushing traffic with packets that destination network is
172.16.2.0/24
and we have 100% cpu with pps below:
bwm-ng v0.6.1 (probing every 0.500s), press 'h' for help
input: /proc/net/dev type: rate
| iface Rx Tx Total
==============================================================================
vlan1002: 0.00 P/s 1.99 P/s
1.99 P/s
vlan1001: 0.00 P/s 717227.12 P/s 717227.12 P/s
enp175s0f0: 2713679.25 P/s 0.00 P/s 2713679.25 P/s
vlan1000: 0.00 P/s 716145.44 P/s 716145.44 P/s
------------------------------------------------------------------------------
total: 2713679.25 P/s 1433374.50 P/s 4147054.00 P/s
with perf top:
PerfTop: 218506 irqs/sec kernel:99.7% exact: 0.0% [4000Hz
cycles], (all, 56 CPUs)
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
91.45% [kernel] [k] queued_spin_lock_slowpath
1.71% [kernel] [k] queued_write_lock_slowpath
0.46% [kernel] [k] ip_finish_output2
0.44% [mlx5_core] [k] mlx5e_handle_rx_cqe
0.43% [kernel] [k] fib_table_lookup
0.40% [kernel] [k] do_raw_spin_lock
0.35% [kernel] [k] __neigh_event_send
0.33% [kernel] [k] dst_release
0.26% [kernel] [k] queued_write_lock
0.22% [mlx5_core] [k] mlx5_cqwq_get_cqe
0.22% [mlx5_core] [k] mlx5e_xmit
0.19% [kernel] [k] virt_to_head_page
0.18% [kernel] [k] page_frag_free
[...]
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