netdev - Re: 100% CPU load when generating traffic to destination network that nexthop is not reachable

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Message-ID: <alpine.LFD.2.20.1708160108050.2947@ja.home.ssi.bg>
Date:   Wed, 16 Aug 2017 01:11:21 +0300 (EEST)
From:   Julian Anastasov <ja@....bg>
To:     Eric Dumazet <eric.dumazet@...il.com>
cc:     Paweł Staszewski <pstaszewski@...are.pl>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: 100% CPU load when generating traffic to destination network
 that nexthop is not reachable


	Hello,

On Wed, 16 Aug 2017, Julian Anastasov wrote:

> 	I thought about this, it is possible in
> neigh_event_send:
> 
>         if (neigh->used != now)
>                 neigh->used = now;
> 	else if (neigh->nud_state == NUD_INCOMPLETE &&
> 		 neigh->arp_queue_len_bytes + skb->truesize >
> 		 NEIGH_VAR(neigh->parms, QUEUE_LEN_BYTES)

	With kfree_skb(skb) here, of course...

> 		return 1;
> 
> 	But this is really in fast path and not sure it is
> worth it. May be if we can move it somehow in __neigh_event_send
> but as neigh->used is changed early we need a better idea
> how to reduce the arp_queue hit rate...

Regards

--
Julian Anastasov <ja@....bg>