Re: [E1000-devel] Slower performance on E5 than i7?

[Ben G. <gr...@ca...>]

On 09/20/2013 11:14 PM, Waskiewicz Jr, Peter P wrote:
> On Fri, 2013-09-20 at 20:51 -0700, Ben Greear wrote:
>> We have been seeing across-the-board network performance issues
>> with the E5 2643 v/s an I7-980.
>> We've been trying ixgbe, igb, and 'veth' virtual devices.
>>
>> Driven by user space or pktgen, the E5 is usually slower by
>> a noticeable bit.  We did disable the VTD BIOS thing that really
>> kills performance, but perhaps there are other BIOS things we
>> should tune in the E5 system?
>>
>> We tried various kernels back to about 3.0 and the general
>> slowness remains.
>>
>> Has anyone done similar comparisons and seen issues?
>
> If I'm not mistaken, the E5 has a lower max frequency than the desktop
> parts.  What I suspect is you're seeing your workloads physically run
> faster on the I7 due to turbo pushing the core past 3 GHz, but the E5 I
> think hovers in the 2.5-3.0 range.

The E5 claims 3.3Ghz.  The i7 is a bit faster, but not that much (the slightly
slower I7-975 out performs it as well).

For all our testing we are running extended loads, so I'm guessing the
temporary turbo boost will not have much effect on our testing.


> Other factors could be how memory is populated in both systems.  Are you
> sure all channels are populated in both systems?

Both systems have 4x4GB sticks...I *think* it is fully populated.

It seems to me that the E5 is more susceptible to cache issues...for instance
if everything is *just* right, the E5 can come close to pushing full tx + rx
on 4 x 10G ports using pktgen, but if softirqd twiddles with things performance
will degrade significantly.  The same issues are seen on the i7, but it seems to
a much less degree.  One of our engineers found some cache thing to disable in
the E5 system's BIOS that gave another 15% improvement, but I don't have the
details at this time.

> This is just some of the quick low-hanging fruit I can think of now.

I appreciate the help.  Is there a current suggested replacement for the I7
(since they seem to be mostly end-of-life)?

Thanks,
Ben

>
> Cheers,
> -PJ
>


-- 
Ben Greear <gr...@ca...>
Candela Technologies Inc  http://www.candelatech.com