From: Eric Dumazet <eric.dumazet@gmail.com>
To: David Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH] neigh: replace unres_qlen by unres_qlen_bytes
Date: Wed, 09 Nov 2011 08:55:25 +0100 [thread overview]
Message-ID: <1320825325.26025.51.camel@edumazet-laptop> (raw)
In-Reply-To: <20111109.001843.1753987502002673227.davem@davemloft.net>
Le mercredi 09 novembre 2011 à 00:18 -0500, David Miller a écrit :
> From: Eric Dumazet <eric.dumazet@gmail.com>
> Date: Wed, 09 Nov 2011 01:14:16 +0100
>
> > unres_qlen is the number of frames we are able to queue per unresolved
> > neighbour. Its default value (3) was never changed and is responsible
> > for strange drops, especially if IP fragments are used, or multiple
> > sessions start in parallel. TCP initial congestion window is now bigger
> > than 3.
>
> BTW, it has been observed in practice that if a long living connection
> suddently sends a burst of traffic after a very long idle period
> (hitting ARP expiry) or something invalidates the ARP entry in use, we
> will drop frames. Because even if the ARP reply comes "fast" it's
> never quick enough to beat the burst of frames.
>
> And if this happens in a scenerio where such lost packets potentially
> mean lost money...
I'll submit a more complete patch, including a fallback support of
unres_qlen, and one missing initializer in nl_ntbl_parm_policy[]
+ [NDTPA_QUEUE_LENBYTES] = { .type = NLA_U32 },
next prev parent reply other threads:[~2011-11-09 7:55 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-08 20:11 [PATCH] neigh: increase unres_qlen by one magnitude Eric Dumazet
2011-11-08 22:24 ` David Miller
2011-11-08 22:45 ` Eric Dumazet
2011-11-08 22:48 ` David Miller
2011-11-09 0:14 ` [PATCH] neigh: replace unres_qlen by unres_qlen_bytes Eric Dumazet
2011-11-09 1:05 ` Stephen Hemminger
2011-11-09 5:18 ` David Miller
2011-11-09 7:55 ` Eric Dumazet [this message]
2011-11-09 11:04 ` [PATCH V3 net-next] neigh: new unresolved queue limits Eric Dumazet
2011-11-09 11:10 ` Eric Dumazet
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