[dpdk-users] Dpdk poor performance on virtual machine

[edgar helmut]

That's what I afraid.
In fact i need the host to back the entire guest's memory with hugepages.
I will find the way to do that and make the testing again.


On 16 Dec 2016 3:14 AM, "Hu, Xuekun" <xuekun.hu at intel.com> wrote:

> You said VM’s memory was 6G, while transparent hugepages was only used ~4G
> (4360192KB). So some were mapped to 4K pages.
>
>
>
> BTW, the memory used by transparent hugepage is not the hugepage you
> reserved in kernel boot option.
>
>
>
> *From:* edgar helmut [mailto:helmut.edgar100 at gmail.com]
> *Sent:* Friday, December 16, 2016 1:24 AM
> *To:* Hu, Xuekun
> *Cc:* Wiles, Keith; users at dpdk.org
> *Subject:* Re: [dpdk-users] Dpdk poor performance on virtual machine
>
>
>
> in fact the vm was created with 6G RAM, its kernel boot args are defined
> with 4 hugepages of 1G each, though when starting the vm i noted that
> anonhugepages increased.
>
> The relevant qemu process id is 6074, and the following sums the amount of
> allocated AnonHugePages:
> sudo grep -e AnonHugePages  /proc/6074/smaps | awk  '{ if($2>0) print $2}
> '|awk '{s+=$1} END {print s}'
>
> which results with 4360192
>
> so not all the memory is backed with transparent hugepages though it is
> more than the amount of hugepages the guest supposed to boot with.
>
> How can I be sure that the required 4G hugepages are really allocated?,
> and not, for example, only 2G out of the 4G are allocated (and the rest 2
> are mapping of the default 4K)?
>
>
>
> thanks
>
>
>
> On Thu, Dec 15, 2016 at 4:33 PM, Hu, Xuekun <xuekun.hu at intel.com> wrote:
>
> Are you sure the anonhugepages size was equal to the total VM's memory
> size?
> Sometimes, transparent huge page mechanism doesn't grantee the app is using
> the real huge pages.
>
>
>
> -----Original Message-----
> From: users [mailto:users-bounces at dpdk.org] On Behalf Of edgar helmut
> Sent: Thursday, December 15, 2016 9:32 PM
> To: Wiles, Keith
> Cc: users at dpdk.org
> Subject: Re: [dpdk-users] Dpdk poor performance on virtual machine
>
> I have one single socket which is Intel(R) Xeon(R) CPU E5-2640 v4 @
> 2.40GHz.
>
> I just made two more steps:
> 1. setting iommu=pt for better usage of the igb_uio
> 2. using taskset and isolcpu so now it looks like the relevant dpdk cores
> use dedicated cores.
>
> It improved the performance though I still see significant difference
> between the vm and the host which I can't fully explain.
>
> any further idea?
>
> Regards,
> Edgar
>
>
> On Thu, Dec 15, 2016 at 2:54 PM, Wiles, Keith <keith.wiles at intel.com>
> wrote:
>
> >
> > > On Dec 15, 2016, at 1:20 AM, edgar helmut <helmut.edgar100 at gmail.com>
> > wrote:
> > >
> > > Hi.
> > > Some help is needed to understand performance issue on virtual machine.
> > >
> > > Running testpmd over the host functions well (testpmd forwards 10g
> > between
> > > two 82599 ports).
> > > However same application running on a virtual machine over same host
> > > results with huge degradation in performance.
> > > The testpmd then is not even able to read 100mbps from nic without
> drops,
> > > and from a profile i made it looks like a dpdk application runs more
> than
> > > 10 times slower than over host…
> >
> > Not sure I understand the overall setup, but did you make sure the
> NIC/PCI
> > bus is on the same socket as the VM. If you have multiple sockets on your
> > platform. If you have to access the NIC across the QPI it could explain
> > some of the performance drop. Not sure that much drop is this problem.
> >
> > >
> > > Setup is ubuntu 16.04 for host and ubuntu 14.04 for guest.
> > > Qemu is 2.3.0 (though I tried with a newer as well).
> > > NICs are connected to guest using pci passthrough, and guest's cpu is
> set
> > > as passthrough (same as host).
> > > On guest start the host allocates transparent hugepages (AnonHugePages)
> > so
> > > i assume the guest memory is backed with real hugepages on the host.
> > > I tried binding with igb_uio and with uio_pci_generic but both results
> > with
> > > same performance.
> > >
> > > Due to the performance difference i guess i miss something.
> > >
> > > Please advise what may i miss here?
> > > Is this a native penalty of qemu??
> > >
> > > Thanks
> > > Edgar
> >
> > Regards,
> > Keith
> >
> >
>
>
>