netdev - Re: Big performance loss from 3.4.63 to 3.10.13 when routing ipv4

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Message-ID: <20131023122600.GB22316@secunet.com>
Date:	Wed, 23 Oct 2013 14:26:00 +0200
From:	Steffen Klassert <steffen.klassert@...unet.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Wolfgang Walter <linux@...m.de>,
	David Miller <davem@...emloft.net>, hannes@...essinduktion.org,
	netdev@...r.kernel.org, klassert@...hematik.tu-chemnitz.de
Subject: Re: Big performance loss from 3.4.63 to 3.10.13 when routing ipv4

On Wed, Oct 23, 2013 at 05:00:01AM -0700, Eric Dumazet wrote:
> On Wed, 2013-10-23 at 13:33 +0200, Wolfgang Walter wrote:
> 
> > I don't know what this value actually means. But on 3.4.x it is much higher. 
> > On a machine with 512MB ram it is 32768, on a machine with 1GB ram it is 
> > 262144 and with 16GB ram it is 4194304.
> > 
> 
> Such huge values should not be needed. We should have at most one dst
> per packet in flight.

We have one cache entry for each packet flow we have already seen.
So a static value should be not too high, because remote entities
can control how many cache entries we have, similar to the routing
cache.

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