netdev - Re: bonding: flow control regression [was Re: bridging: flow control regression]

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Message-ID: <20101102084646.GA23774@verge.net.au>
Date:	Tue, 2 Nov 2010 17:46:48 +0900
From:	Simon Horman <horms@...ge.net.au>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org, Jay Vosburgh <fubar@...ibm.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: bonding: flow control regression [was Re: bridging: flow
 control regression]

On Tue, Nov 02, 2010 at 08:30:57AM +0100, Eric Dumazet wrote:
> Le mardi 02 novembre 2010 à 16:03 +0900, Simon Horman a écrit :
> > On Tue, Nov 02, 2010 at 05:53:42AM +0100, Eric Dumazet wrote:
> > > Le mardi 02 novembre 2010 à 11:06 +0900, Simon Horman a écrit :
> > > 
> > > > Thanks for the explanation.
> > > > I'm not entirely sure how much of a problem this is in practice.
> > > 
> > > Maybe for virtual devices (tunnels, bonding, ...), it would make sense
> > > to delay the orphaning up to the real device.
> > 
> > That was my initial thought. Could you give me some guidance
> > on how that might be done so I can try and make a patch to test?
> > 
> > > But if the socket send buffer is very large, it would defeat the flow
> > > control any way...
> > 
> > I'm primarily concerned about a situation where
> > UDP packets are sent as fast as possible, indefinitely.
> > And in that scenario, I think it would need to be a rather large buffer.
> > 
> 
> Please try following patch, thanks.

Thanks Eric, that seems to resolve the problem that I was seeing.

With your patch I see:

No bonding

# netperf -c -4 -t UDP_STREAM -H 172.17.60.216 -l 30 -- -m 1472
UDP UNIDIRECTIONAL SEND TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 172.17.60.216 (172.17.60.216) port 0 AF_INET
Socket  Message  Elapsed      Messages                   CPU      Service
Size    Size     Time         Okay Errors   Throughput   Util     Demand
bytes   bytes    secs            #      #   10^6bits/sec % SU     us/KB

116736    1472   30.00     2438413      0      957.2     8.52     1.458 
129024           30.00     2438413             957.2     -1.00    -1.000

With bonding (one slave, the interface used in the test above)

netperf -c -4 -t UDP_STREAM -H 172.17.60.216 -l 30 -- -m 1472
UDP UNIDIRECTIONAL SEND TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 172.17.60.216 (172.17.60.216) port 0 AF_INET
Socket  Message  Elapsed      Messages                   CPU      Service
Size    Size     Time         Okay Errors   Throughput   Util     Demand
bytes   bytes    secs            #      #   10^6bits/sec % SU     us/KB

116736    1472   30.00     2438390      0      957.1     8.97     1.535 
129024           30.00     2438390             957.1     -1.00    -1.000

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