netdev - Re: [PATCH 5/5] bonding: Add tlb_dynamic

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Message-ID: <1396281602.29410.44.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Mon, 31 Mar 2014 09:00:02 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Mahesh Bandewar <maheshb@...gle.com>
Cc:	Jay Vosburgh <fubar@...ibm.com>,
	Veaceslav Falico <vfalico@...hat.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Maciej Zenczykowski <maze@...gle.com>
Subject: Re: [PATCH 5/5] bonding: Add tlb_dynamic_lb module parameter

On Fri, 2014-03-28 at 22:29 -0700, Mahesh Bandewar wrote:
> The aggresive load balancing causes packet re-ordering as active
> flows are moved from a slave to another within the group. Sometime
> this aggresive lb is not necessary if the preference is for less
> re-ordering. This module parameter if used with value "0" disables
> this dynamic flow shuffling minimizing packet re-ordering. Of course
> the side effect is that it has to live with the static load balancing
> that the hashing distribution provides. This impact is less severe if
> the correct xmit-hashing-policy is used for the tlb setup.
> 
> The default value of the parameter is set to "1" mimicing the earlier
> behavior.
> 
> Ran the netperf test with 200 stream for 1 min between two hosts with
> 4x1G trunk (xmit-lb mode with xmit-policy L3+4) before and after these
> changes. Following was the command used for those 200 instances -
> 
>     netperf -t TCP_RR -l 60 -s 5 -H <host> -- -r1,1024

There is reordering potential in this workload, as we have at most one
packet containing payload in flight ?

> 
> Transactions per second:
>     Before changes: 109250
>     After  changes: 113752
> 
> Signed-off-by: Mahesh Bandewar <maheshb@...gle.com>
> ---

>  			      "each slaves peer switch. The default is 1.");
> +module_param(tlb_dynamic_lb, int, 0644);
> +MODULE_PARM_DESC(tlb_dynamic_lb, "Enable periodic flow balancing. "
> +				 "The default is 1.");

I am a bit unsure why we need to add a new global parameter.

If the tlb_dynamic_lb can be dynamically changed on a bonding device,
why adding this ?



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