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Date: Mon, 26 Aug 2013 16:46:01 +0200
From: Luigi Rizzo <rizzo@iet.unipi.it>
To: Andre Oppermann <andre@freebsd.org>
Subject: Re: route/arp lifetime (Re: it's the output, not ack coalescing
 (Re: TSO and FreeBSD vs Linux))
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Cc: FreeBSD Net <freebsd-net@freebsd.org>, Adrian Chadd <adrian@freebsd.org>,
 "Alexander V. Chernikov" <melifaro@ipfw.ru>
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On Mon, Aug 26, 2013 at 04:27:59PM +0200, Andre Oppermann wrote:
...
> 
> 1. lle lock to rmlock.
> 
> 2. if_addr and IN_ADDR locks to rmlocks.
> 
> 3. routing table locking (rmlocks, and by doing away with rtentry locks and refcounting
>     through copy-out on lookup and prohibition of having any pointers into the rtable).

re. the last item, the problem is that we need to access *ifp
after the route lookup, and this cannot be solved with a copy-on-lookup
(I guess at the moment the rte has a refcounted pointer to the ifp).

This is why i argued that it might be useful to cache into the socket a
refcounted pointer into the ifp (or rte) and update it lazily
(periodically or through generation counters).

cheers
luigi