netdev - Re: Fwd: Linux stack performance drop (TCP and UDP) in 3.10 kernel in routed scenario

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Date:	Wed, 04 Jun 2014 11:44:18 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	sowmini varadhan <sowmini05@...il.com>
Cc:	Suprasad Mutalik Desai <suprasad.desai@...il.com>,
	netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.ne>
Subject: Re: Fwd: Linux stack performance drop (TCP and UDP) in 3.10 kernel
 in routed scenario

On Wed, 2014-06-04 at 14:26 -0400, sowmini varadhan wrote:
> On Wed, Jun 4, 2014 at 10:59 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> 
> > Problem with IPv4 route cache is that is was too easy to flood it and
> > get worse performance.
> >
> > It had simply huge memory costs, and non predictable behavior [1]
> 
> Can you elaborate? Caches usually have an upper bound on
> the memory to be consumed by the cache, and from my reading
> of the 2.6.32 code, seems like it also had such limits (there was
> a sysctl tunable to turn off hashing, and rt_intern_hash() also had
> other bounds. Were these not enough?


http://vger.kernel.org/~davem/columbia2012.pdf


For gory details :

git log net/ipv4/route.c



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