netdev - Re: under-performing bonded interfaces

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Message-ID: <CANj2Eben0hrP6KwxyA1WPqiqzm84w=J2_sdtrKtGvxdftuksqg@mail.gmail.com>
Date:	Wed, 21 Dec 2011 20:26:04 -0500
From:	Simon Chen <simonchennj@...il.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	Ben Greear <greearb@...delatech.com>, netdev@...r.kernel.org
Subject: Re: under-performing bonded interfaces

Hi folks,

I added an Intel X520 card to both the sender and receiver... Now I
have two 10G ports on a PCIe 2.0 x8 slot (5Gx8), so the bandwidth of
the PCI bus shouldn't be the bottleneck.

Now the throughput test gives me around 16Gbps in aggregate. Any ideas
how I can push closer to 20G? I don't quite understand where the
bottleneck is now.

Thanks.
-Simon

On Wed, Nov 16, 2011 at 9:51 PM, Ben Hutchings
<bhutchings@...arflare.com> wrote:
> On Wed, 2011-11-16 at 20:38 -0500, Simon Chen wrote:
>> Thanks, Ben. That's good discovery...
>>
>> Are you saying that both 10G NICs are on the same PCIe x4 slot, so
>> that they're subject to the 12G throughput bottleneck?
>
> I assumed you were using 2 ports on the same board, i.e. the same slot.
> If you were using 1 port each of 2 boards then I would have expected
> them both to be usable at full speed.  So far as I can remember, PCIe
> bridges are usually set up so there isn't contention for bandwidth
> between slots.
>
> Ben.
>
> --
> Ben Hutchings, Staff Engineer, Solarflare
> Not speaking for my employer; that's the marketing department's job.
> They asked us to note that Solarflare product names are trademarked.
>
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