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Message-ID: <d54b2cce-db22-0c9c-2fca-708a682b4b65@itcare.pl>
Date: Wed, 16 Aug 2017 12:07:24 +0200
From: Paweł Staszewski <pstaszewski@...are.pl>
To: Julian Anastasov <ja@....bg>, Eric Dumazet <eric.dumazet@...il.com>
Cc: Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: 100% CPU load when generating traffic to destination network that
nexthop is not reachable
Hi
Patch applied - but no big change - from 0.7Mpps per vlan to 1.2Mpps per
vlan
previously(without patch) 100% cpu load:
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 patch (100% cpu load a little better pps performance)
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 1.00 P/s
1.00 P/s
vlan1001: 0.00 P/s 1202161.50 P/s 1202161.50 P/s
enp175s0f0: 3699864.50 P/s 0.00 P/s 3699864.50 P/s
vlan1000: 0.00 P/s 1196870.38 P/s 1196870.38 P/s
------------------------------------------------------------------------------
total: 3699864.50 P/s 2399033.00 P/s 6098897.50 P/s
perf top attached below:
1.90% 0.00% ksoftirqd/39 [kernel.vmlinux] [k] run_ksoftirqd
|
--1.90%--run_ksoftirqd
|
--1.90%--__softirqentry_text_start
|
--1.90%--net_rx_action
|
--1.90%--mlx5e_napi_poll
|
--1.89%--mlx5e_poll_rx_cq
|
--1.88%--mlx5e_handle_rx_cqe
|
--1.85%--napi_gro_receive
|
--1.85%--netif_receive_skb_internal
|
--1.85%--__netif_receive_skb
|
--1.85%--__netif_receive_skb_core
|
--1.85%--ip_rcv
|
--1.85%--ip_rcv_finish
|
--1.83%--ip_forward
|
--1.82%--ip_forward_finish
|
--1.82%--ip_output
|
--1.82%--ip_finish_output
|
--1.82%--ip_finish_output2
|
--1.79%--neigh_resolve_output
|
--1.77%--neigh_event_send
|
--1.77%--__neigh_event_send
|
--1.74%--_raw_write_lock_bh
|
--1.74%--queued_write_lock
queued_write_lock_slowpath
|
--1.70%--queued_spin_lock_slowpath
1.90% 0.00% ksoftirqd/34 [kernel.vmlinux] [k]
__softirqentry_text_start
|
---__softirqentry_text_start
|
--1.90%--net_rx_action
|
--1.90%--mlx5e_napi_poll
|
--1.89%--mlx5e_poll_rx_cq
|
--1.88%--mlx5e_handle_rx_cqe
|
--1.86%--napi_gro_receive
|
--1.85%--netif_receive_skb_internal
|
--1.85%--__netif_receive_skb
|
--1.85%--__netif_receive_skb_core
|
--1.85%--ip_rcv
|
--1.85%--ip_rcv_finish
|
--1.83%--ip_forward
|
--1.82%--ip_forward_finish
|
--1.82%--ip_output
|
--1.82%--ip_finish_output
|
--1.82%--ip_finish_output2
|
--1.79%--neigh_resolve_output
|
--1.77%--neigh_event_send
|
--1.77%--__neigh_event_send
|
--1.74%--_raw_write_lock_bh
queued_write_lock
queued_write_lock_slowpath
|
--1.71%--queued_spin_lock_slowpath
1.85% 0.00% ksoftirqd/38 [kernel.vmlinux] [k]
ip_rcv_finish
|
--1.85%--ip_rcv_finish
|
--1.83%--ip_forward
|
--1.82%--ip_forward_finish
|
--1.82%--ip_output
|
--1.82%--ip_finish_output
|
--1.82%--ip_finish_output2
|
--1.79%--neigh_resolve_output
|
--1.77%--neigh_event_send
|
--1.77%--__neigh_event_send
|
--1.74%--_raw_write_lock_bh
queued_write_lock
queued_write_lock_slowpath
|
--1.71%--queued_spin_lock_slowpath
1.85% 0.00% ksoftirqd/22 [kernel.vmlinux] [k] ip_rcv
|
--1.85%--ip_rcv
|
--1.85%--ip_rcv_finish
|
--1.83%--ip_forward
|
--1.82%--ip_forward_finish
|
--1.82%--ip_output
|
--1.82%--ip_finish_output
|
--1.82%--ip_finish_output2
|
--1.79%--neigh_resolve_output
|
--1.77%--neigh_event_send
|
--1.77%--__neigh_event_send
|
--1.73%--_raw_write_lock_bh
queued_write_lock
queued_write_lock_slowpath
|
--1.70%--queued_spin_lock_slowpath
1.83% 0.00% ksoftirqd/9 [kernel.vmlinux] [k]
ip_forward
|
--1.83%--ip_forward
|
--1.82%--ip_forward_finish
|
--1.82%--ip_output
|
--1.82%--ip_finish_output
|
--1.82%--ip_finish_output2
|
--1.79%--neigh_resolve_output
|
--1.77%--neigh_event_send
|
--1.77%--__neigh_event_send
|
--1.74%--_raw_write_lock_bh
queued_write_lock
queued_write_lock_slowpath
|
--1.70%--queued_spin_lock_slowpath
1.82% 0.00% ksoftirqd/35 [kernel.vmlinux] [k]
ip_output
|
--1.82%--ip_output
|
--1.82%--ip_finish_output
|
--1.82%--ip_finish_output2
|
--1.79%--neigh_resolve_output
|
--1.77%--neigh_event_send
|
--1.77%--__neigh_event_send
|
--1.74%--_raw_write_lock_bh
queued_write_lock
queued_write_lock_slowpath
|
--1.71%--queued_spin_lock_slowpath
1.82% 0.00% ksoftirqd/38 [kernel.vmlinux] [k]
ip_finish_output
|
--1.82%--ip_finish_output
|
--1.82%--ip_finish_output2
|
--1.79%--neigh_resolve_output
|
--1.77%--neigh_event_send
|
--1.77%--__neigh_event_send
|
--1.74%--_raw_write_lock_bh
queued_write_lock
queued_write_lock_slowpath
|
--1.71%--queued_spin_lock_slowpath
1.82% 0.00% ksoftirqd/37 [kernel.vmlinux] [k]
ip_forward_finish
|
--1.82%--ip_forward_finish
ip_output
|
--1.82%--ip_finish_output
|
--1.82%--ip_finish_output2
|
--1.79%--neigh_resolve_output
|
--1.76%--neigh_event_send
__neigh_event_send
|
--1.73%--_raw_write_lock_bh
queued_write_lock
queued_write_lock_slowpath
|
--1.70%--queued_spin_lock_slowpath
W dniu 2017-08-16 o 09:42, Julian Anastasov pisze:
> Hello,
>
> On Tue, 15 Aug 2017, Eric Dumazet wrote:
>
>> It must be possible to add a fast path without locks.
>>
>> (say if jiffies has not changed before last state change)
> New day - new idea. Something like this? But it
> has bug: without checking neigh->dead under lock we don't
> have the right to access neigh->parms, it can be destroyed
> immediately by neigh_release->neigh_destroy->neigh_parms_put->
> neigh_parms_destroy->kfree. Not sure, may be kfree_rcu can help
> for this...
>
> diff --git a/include/net/neighbour.h b/include/net/neighbour.h
> index 9816df2..f52763c 100644
> --- a/include/net/neighbour.h
> +++ b/include/net/neighbour.h
> @@ -428,10 +428,10 @@ static inline int neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
> {
> unsigned long now = jiffies;
>
> - if (neigh->used != now)
> - neigh->used = now;
> if (!(neigh->nud_state&(NUD_CONNECTED|NUD_DELAY|NUD_PROBE)))
> return __neigh_event_send(neigh, skb);
> + if (neigh->used != now)
> + neigh->used = now;
> return 0;
> }
>
> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 16a1a4c..52a8718 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -991,8 +991,18 @@ static void neigh_timer_handler(unsigned long arg)
>
> int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
> {
> - int rc;
> bool immediate_probe = false;
> + unsigned long now = jiffies;
> + int rc;
> +
> + if (neigh->used != now) {
> + neigh->used = now;
> + } else if (neigh->nud_state == NUD_INCOMPLETE &&
> + (!skb || neigh->arp_queue_len_bytes + skb->truesize >
> + NEIGH_VAR(neigh->parms, QUEUE_LEN_BYTES))) {
> + kfree_skb(skb);
> + return 1;
> + }
>
> write_lock_bh(&neigh->lock);
>
> @@ -1005,7 +1015,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
> if (!(neigh->nud_state & (NUD_STALE | NUD_INCOMPLETE))) {
> if (NEIGH_VAR(neigh->parms, MCAST_PROBES) +
> NEIGH_VAR(neigh->parms, APP_PROBES)) {
> - unsigned long next, now = jiffies;
> + unsigned long next;
>
> atomic_set(&neigh->probes,
> NEIGH_VAR(neigh->parms, UCAST_PROBES));
>
> Regards
>
> --
> Julian Anastasov <ja@....bg>
>
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