Hi, I have 2 VCPUs assigned to the VM. I thought more CPUs wouldn't really help
because a single TCP connection doesn't span across cores anyway? I would have
to run multiple connections simultaneously I think.
I use the standard packet size, I don't do jumbo frames or anything. I don't
tweak the OS either, I just want to see how it would perform by default.
I'm just surprised that CPU isn't maxed out at all. It must be because
polling/NAPI is too slow fetching packets? It must be a timer thing like this?
Otherwise, is it that hardware resources are limited with just a single queue
and the RX ring buffer cannot be filled/refilled quickly enough? Why else would
it be slow if CPU resources are there.
When I say maxed out I mean the VCPU of course, so those cores are not running
at full capability.
Anna
</div>
-----Original Message-----
From: "Waskiewicz Jr, Peter P" <[email protected]>
Date: Thu, 28 Jun 2012 08:45:23
To: Fischer, Anna<[email protected]>
Cc: [email protected]<[email protected]>
Subject: Re: [E1000-devel] 82599 receive performance
Hi Anna,
On Thu, 2012-06-28 at 08:32 +0000, Fischer, Anna wrote:
> Hi, I'm running a 10G 82599 controller in PCI SR-IOV mode, and the VF is
> assigned to a VM (PCI pass-through). I only enable a single VF (max_vfs=1).
> On my machine I run KVM and just a single VM.
> The machine has 4 Xeon X5550 cores.
>
> I've tested RX and TX throughput using iperf (TCP). Basically I want to see
> how fast I can send and receive packets to/from the VM.
How many CPU's are provisioned to your VM? Also, what packet size are
you using with iperf? In many cases, a single Rx/Tx queue pair is not
enough to run 10GbE line rate.
-PJ
> TX performance comes to about 8.5Gbps. At that point, CPU is maxed out.
>
> RX performance only comes to about 5.5Gbps. CPU isn't maxed out at all, and I
> wonder, if this is the expected RX throughput? I have to say that I only run
> a single TX queue and a single RX queue. (I am testing against something else
> that also just runs a single queue, so I need to keep it fair.) I haven't
> tuned any OS parameters, I run Fedora Core 16 and a 3.4 Linux kernel.
>
> Thanks,
> Anna
>
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