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

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Date:	Mon, 31 Mar 2014 14:47:27 -0700
From:	Mahesh Bandewar <maheshb@...gle.com>
To:	Eric Dumazet <eric.dumazet@...il.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 Mon, Mar 31, 2014 at 9:00 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> 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 ?
>
I'll run the numbers again with a different work-load like -r80k,80k
and append it to the commit msg.
> >
> > 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 ?
>
 I was trying to be in sync with most of the values currently set.
Also thinking behind this was to set the initial value through the
module parameter and the per-bond value can be altered if needed using
the per-device entry.
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