netdev - Re: ARP garbage collection issues in 3.1?

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Message-ID: <20111102210731.281c3277@kryten>
Date:	Wed, 2 Nov 2011 21:07:31 +1100
From:	Anton Blanchard <anton@...ba.org>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: ARP garbage collection issues in 3.1?


Hi Dave,

> > Any ideas how we could make this behave a bit better? I know setting
> > gc_thresh3 higher is the ultimate solution, but if gc_thresh1 and
> > gc_thresh2 are always below the route threshold we should either fix
> > this issue or remove them completely.
> 
> The solution is to do refcount'less RCU lookups into the neigh
> tables on every packet send, and long term that's what I intend
> to implement.
> 
> That's what's behind making the recent change to make the ARP hash
> cheaper etc.
> 
> See slides 5, 6, and 7 in:
> 
> http://vger.kernel.org/netconf2011_slides/davem_netconf2011.pdf
> 
> Once that's done you can trim whatever neigh entries you want,
> whenever you want.
> 
> You are right that the current situation is silly, because if
> we're willing to commit to N routing table entries we might as
> well be willing to commit to N arp table entries as well.

Thanks for clearing it up! Looking forwards to the new scheme :)

Anton
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