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" <[email protected]> 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:[email protected]] > *Sent:* Friday, December 16, 2016 1:24 AM > *To:* Hu, Xuekun > *Cc:* Wiles, Keith; [email protected] > *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 <[email protected]> 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:[email protected]] On Behalf Of edgar helmut > Sent: Thursday, December 15, 2016 9:32 PM > To: Wiles, Keith > Cc: [email protected] > 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 <[email protected]> > wrote: > > > > > > On Dec 15, 2016, at 1:20 AM, edgar helmut <[email protected]> > > 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 > > > > > > >
