network performance analysis in virtualized environments · network activities in virtual...

Network performance analysis in virtualized environments

Adel Belkhiri Michel DagenaisDecember 6, 2018

Polytechnique Montréal

Laboratoire DORSAL

POLYTECHNIQUE MONTREAL – Adel Belkhiri

Introduction– Previously on vGPU analysis

– Network virtualization analysis

Literature review

Preliminary investigations

Conclusion

2

Agenda

POLYTECHNIQUE MONTREAL – Adel Belkhiri 3

Previously on vGPU analysis

● Gvt-g is a full GPU virtualization product for Intel GPUs (Haswell architecture and up) :

● Gvt-g : Graphics Virtualization Technology- grid

● KvmGT is a version of Gvt-g for KVM

● Performance analysis of I/O operations in virtual machines.

Tracing framework for the performance analysis of vGPU-enabled VMs created with KvmGT

POLYTECHNIQUE MONTREAL – Adel Belkhiri 4

Control Flow view of GPU requests

Per-engine GPU occupancy

Previously on vGPU analysis

virtual GPU occupancy

Per-process GPU occupancy


● Traditional network monitoring tools (such as Tcpdump) are incapable of monitoring network activities in virtual environments (cloud computing) :

● Incapacity to detect data exchanged between collocated VMs

● Incompatibility with some properties of cloud computing (live migration, etc.)

● Performance metrics not adapted to virtual networks specificities.

5

Network virtualization analysis

Context of the current topic :


1) Profile different technologies used in networking virtualization : Virtio-net, auto-virtualized network cards, Open vSwitch, etc.

2) Analyze the performance of virtualized networks based on performance metrics relevant to virtualized environments.

3) Understand the latencies caused by packet flow processing, where one of the two endpoints is a VM, and identify bottlenecks.

Motivation :

6

Network virtualization analysis


Introduction

Literature review– NIC virtualization

– Switch/router virtualization


Conclusion

7

Agenda


Technologies used in NIC virtualization

NIC Virtualization

8


● Para-virtualization

● Virtio is a standard interface through which a module of the guest OS could exchange data with a module of the host OS using shared memory (ring buffer).

● Virtio-net uses the Virtio framework to create a paravirtualized network interface, at the user-space level (QEMU).

● Virtio-net limitations : Poor performance due to frequent context switches between host OS, QEMU and guest OS.

NIC Virtualization

9


virtio-net vs. vhost-net

Kernel

QEMU

Virtual Machine

virtio buffers

Hardware

Tap

virtio net

1

2

3Kernel

QEMU

Hardware

Tap

2

vhost net

Virtual Machine

virtio buffers

virtio-net vhost-net

NIC Virtualization

10


● Hardware-assisted Virtualization

● VMDq (Virtual Machine Device Queue)

► Sort packets and save them in waiting queues implemented at the hardware level.

► Each waiting queue is associated with a different interruption to allow the hypervisor to distinguish between recipient VMs.

● SR-IOV (Single Root – Input Output Virtualization)

► Reduce the interventions of the hypervisor by copying packets directly in the memory space of the VM.

► High performance.

NIC Virtualization

11


● Hardware-assisted Virtualization

VMDq vs. SR-IOV

VM1

VMM

NIC

VM2 VM3

RX TX

Layer 2 : virtual switch

VM1

VMM

NIC

VM2 VM3

Layer 2 : virtual switch

VM1

VMM

VM2 VM3

RX TX RX TX RX TX

Virtual Bridge and classifier

VF VF VF

NIC

Layer 2 : classifier

VMDq SR-IOVOrdinary NIC

NIC Virtualization

12


● SDN (Software-Defined Networking)

● A new networking architecture which separates, at the hardware level, the plan of network control from the plan of forwarding packets.

● OVS (OpenvSwitch), implements the OpenFlow standard and emulates a switch in many virtualized environments.

Switches virtualization

Réf : https://www.commsbusiness.co.uk/features/software-defined-networking-sdn-explained/

13


Introduction

Literature review

Preliminary investigations– Packets receiving path

– What about tracing ?

Conclusion

Agenda

14


NIC

CPU

ring buffer

RAM

Packets

SKB (socket buffer)

1. received by NIC

2. copy via DMA

3. run IRQ handler

4. suspend IRQ

Driver

Packets receiving path

15

NIC

CPU

ring buffer

RAM

Packets

SKB (Socket Buffers)

napi_gro_receive

netif_receive_skb GRO List

net_rx_action

1. received by NIC2. copy via DMA

3. run IRQ handler 7. trying to combine packets via GRO

8. packets are held and combined

9. forward packet to TCP/IP stack

6. poll () : harvest packets

...

5. run Soft_IRQ handler

4. suspend IRQ

Driver

poll structure


Packets receiving path

16


Packet Rx path

softirq_entry

netif_receive_skb

skb_copy_datagram_iovec

napi_poll

softirq_exit

skb_consume

skb_free

napi_gro_receive

Packet Tx path

softirq_entry

net_dev_start_xmit

net_dev_xmit

softirq_exit

net_dev_queue

What about tracing ?

17


Trace Compass State System

Ongoing work ...

18


Views already developped (in Trace Compass) :

View of TCP sockets based on a pcap trace (tcpdump)

Views that we want to develop :

Ongoing work ...

19


Introduction

Literature review


Conclusion

Agenda

20


● There is a real need for efficient analyses to diagnose problems in virtual networks and identify the root causes of their latencies.

● Tracing tools (such as LTTng) are great to collect the low-level data needed for these analyses.

● Our current challenge is to develop a tracing framework capable of analyzing the performance of traditional networks.

21

Conclusion


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network performance analysis in virtualized environments · network activities in virtual...

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