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From: Rick Jones <rick.jones2@hp.com>
To: David Miller <davem@davemloft.net>
Cc: andi@firstfloor.org, netdev@vger.kernel.org
Subject: Re: small RPS cache for fragments?
Date: Tue, 17 May 2011 15:42:48 -0700	[thread overview]
Message-ID: <1305672168.8149.966.camel@tardy> (raw)
In-Reply-To: <20110517.175044.2057517197524794568.davem@davemloft.net>

On Tue, 2011-05-17 at 17:50 -0400, David Miller wrote:
> From: Andi Kleen <andi@firstfloor.org>
> Date: Tue, 17 May 2011 14:48:28 -0700
> 
> > David Miller <davem@davemloft.net> writes:
> > 
> >> Guys we can't time out fragments if we are not the final
> >> destination.
> > 
> > If you're not the final destination you should never even
> > try to reassemble them?
> > 
> > I'm probably missing something...
> 
> We're discussing the idea to do the defragmentation first
> so we can choose the flow properly and steer the packet
> to the correct cpu.
> 
> This also would allos each fragmented packet to traverse the
> stack only once (one route lookup etc.) instead of once per
> fragment.
> 
> Please read the rest of this thread, we have discussed this
> and now I'm repeating information solely for your benefit.

Well, I should probably be beaten with that stick too because I wasn't
thinking about forwarding, only being the destination system when I
broached the suggestion of doing RFS after reassembly.  I can see where
one *might* be able to do limited RPS when forwarding, but I didn't know
that RFS had been extended to forwarding.

Now though I see why you were rightfully concerned about timeouts -
given all the concerns about added latency from bufferbloat, I wouldn't
think that an additional 10 or perhaps even 1ms timeout on a reassembly
attempt to get the layer four header when forwarding would sit well with
folks - they will expect the fragments to flow through without
additional delay.

rick jones



  parent reply	other threads:[~2011-05-17 22:42 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-05-17 18:33 small RPS cache for fragments? David Miller
2011-05-17 20:02 ` Tom Herbert
2011-05-17 20:17   ` Rick Jones
2011-05-17 20:41     ` Rick Jones
2011-05-17 20:49   ` David Miller
2011-05-17 21:00     ` Eric Dumazet
2011-05-17 21:10       ` David Miller
2011-05-17 21:13         ` Rick Jones
2011-05-17 21:13         ` Ben Hutchings
2011-05-17 21:26           ` David Miller
2011-05-17 21:40             ` Rick Jones
2011-05-17 21:27           ` Eric Dumazet
2011-05-17 21:11       ` Rick Jones
2011-05-17 21:11       ` Ben Hutchings
2011-05-17 21:27     ` Tom Herbert
2011-05-17 21:28       ` David Miller
2011-05-17 23:59     ` Changli Gao
2011-05-18  6:37       ` David Miller
2011-05-17 20:14 ` Eric Dumazet
2011-05-17 20:47   ` David Miller
2011-05-17 21:44   ` Andi Kleen
2011-05-17 21:52     ` Eric Dumazet
2011-05-17 22:03       ` Andi Kleen
2011-05-17 21:44 ` David Miller
2011-05-17 21:48   ` Andi Kleen
2011-05-17 21:50     ` David Miller
2011-05-17 22:06       ` Andi Kleen
2011-05-17 22:42       ` Rick Jones [this message]
2011-05-24 20:01 ` David Miller
2011-05-24 21:38   ` Rick Jones
2011-06-04 20:29     ` David Miller
2011-06-06 17:08       ` Rick Jones
2011-06-06 17:15         ` Eric Dumazet
2011-06-06 18:06           ` Rick Jones
2011-06-06 19:23           ` David Miller
2011-06-06 19:22         ` David Miller
2011-06-06 20:05           ` Rick Jones
2011-06-06 21:06             ` Jay Vosburgh
2011-06-06 21:40               ` David Miller
2011-06-06 22:49                 ` Chris Friesen

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