Skip to main content
Redhat Developers  Logo
  • Products

    Featured

    • Red Hat Enterprise Linux
      Red Hat Enterprise Linux Icon
    • Red Hat OpenShift AI
      Red Hat OpenShift AI
    • Red Hat Enterprise Linux AI
      Linux icon inside of a brain
    • Image mode for Red Hat Enterprise Linux
      RHEL image mode
    • Red Hat OpenShift
      Openshift icon
    • Red Hat Ansible Automation Platform
      Ansible icon
    • Red Hat Developer Hub
      Developer Hub
    • View All Red Hat Products
    • Linux

      • Red Hat Enterprise Linux
      • Image mode for Red Hat Enterprise Linux
      • Red Hat Universal Base Images (UBI)
    • Java runtimes & frameworks

      • JBoss Enterprise Application Platform
      • Red Hat build of OpenJDK
    • Kubernetes

      • Red Hat OpenShift
      • Microsoft Azure Red Hat OpenShift
      • Red Hat OpenShift Virtualization
      • Red Hat OpenShift Lightspeed
    • Integration & App Connectivity

      • Red Hat Build of Apache Camel
      • Red Hat Service Interconnect
      • Red Hat Connectivity Link
    • AI/ML

      • Red Hat OpenShift AI
      • Red Hat Enterprise Linux AI
    • Automation

      • Red Hat Ansible Automation Platform
      • Red Hat Ansible Lightspeed
    • Developer tools

      • Red Hat Trusted Software Supply Chain
      • Podman Desktop
      • Red Hat OpenShift Dev Spaces
    • Developer Sandbox

      Developer Sandbox
      Try Red Hat products and technologies without setup or configuration fees for 30 days with this shared Openshift and Kubernetes cluster.
    • Try at no cost
  • Technologies

    Featured

    • AI/ML
      AI/ML Icon
    • Linux
      Linux Icon
    • Kubernetes
      Cloud icon
    • Automation
      Automation Icon showing arrows moving in a circle around a gear
    • View All Technologies
    • Programming Languages & Frameworks

      • Java
      • Python
      • JavaScript
    • System Design & Architecture

      • Red Hat architecture and design patterns
      • Microservices
      • Event-Driven Architecture
      • Databases
    • Developer Productivity

      • Developer productivity
      • Developer Tools
      • GitOps
    • Secure Development & Architectures

      • Security
      • Secure coding
    • Platform Engineering

      • DevOps
      • DevSecOps
      • Ansible automation for applications and services
    • Automated Data Processing

      • AI/ML
      • Data Science
      • Apache Kafka on Kubernetes
      • View All Technologies
    • Start exploring in the Developer Sandbox for free

      sandbox graphic
      Try Red Hat's products and technologies without setup or configuration.
    • Try at no cost
  • Learn

    Featured

    • Kubernetes & Cloud Native
      Openshift icon
    • Linux
      Rhel icon
    • Automation
      Ansible cloud icon
    • Java
      Java icon
    • AI/ML
      AI/ML Icon
    • View All Learning Resources

    E-Books

    • GitOps Cookbook
    • Podman in Action
    • Kubernetes Operators
    • The Path to GitOps
    • View All E-books

    Cheat Sheets

    • Linux Commands
    • Bash Commands
    • Git
    • systemd Commands
    • View All Cheat Sheets

    Documentation

    • API Catalog
    • Product Documentation
    • Legacy Documentation
    • Red Hat Learning

      Learning image
      Boost your technical skills to expert-level with the help of interactive lessons offered by various Red Hat Learning programs.
    • Explore Red Hat Learning
  • Developer Sandbox

    Developer Sandbox

    • Access Red Hat’s products and technologies without setup or configuration, and start developing quicker than ever before with our new, no-cost sandbox environments.
    • Explore Developer Sandbox

    Featured Developer Sandbox activities

    • Get started with your Developer Sandbox
    • OpenShift virtualization and application modernization using the Developer Sandbox
    • Explore all Developer Sandbox activities

    Ready to start developing apps?

    • Try at no cost
  • Blog
  • Events
  • Videos

A statistics update in Open vSwitch user space datapath

September 18, 2023
David Marchand
Related topics:
LinuxOpen source
Related products:
Red Hat Enterprise Linux

Share:

    With the demands for higher bandwidth, came the need for scaling and processing packets on more CPU resources. In Open vSwitch (OVS) using DPDK for faster IO, this translated to using more receive and transmit queues to allow more PMD threads to process the packets. This adds some complexity to a system not easy to understand in the first place. Support or operation people still want to know how much traffic is received and how it is distributed across the CPU resources. To offer help, this article describes new statistics added for the user space datapath in OVS 2.17 and later.

    Per queue statistics for DPDK ports

    A first evolution in OVS 2.17 consisted of exposing receive and transmit queues statistics per DPDK physical ports in ovsdb.

    For example:

    # ovs-vsctl get interface dpdk0 statistics | sed -e 's#[{}]##g' -e 's#, #\n#g' | grep packets= | grep -v '=0$'
    rx_packets=5553474
    rx_q0_packets=3705290
    rx_q1_packets=1848184
    tx_broadcast_packets=220
    tx_multicast_packets=488
    tx_packets=39406658924
    tx_q1_packets=3700644
    tx_q2_packets=97
    tx_q3_packets=19696490438
    tx_q4_packets=19706467745

    Those per queue statistics require support from the DPDK driver backing the port.

    A vast majority of physical (and even some virtual) NIC DPDK drivers do support those statistics. But if no statistics appear in ovsdb, you may check for support by looking for the RTE_ETH_DEV_AUTOFILL_QUEUE_XSTATS (1 << 6) value in the port dev_flags bitmask through the DPDK telemetry tool (coming with the dpdk-tools rpm).

    For example, check port 0:

    # if [ $(($(echo /ethdev/info,0 | dpdk-telemetry.py -f /var/run/openvswitch/dpdk/rte | jq -r '.["/ethdev/info"]["dev_flags"]') & 64)) != 0 ]; then
      echo per queue stats are supported;
    else
      echo per queue stats may not be implemented for this driver;
    fi
    per queue stats are supported

    Per queue statistics for vhost-user ports

    Getting the same level of information for vhost-user ports has required some reworking in the DPDK vhost-user libary because the library was not accounting such information.


    This was enhanced by the community in the DPDK v22.07 release with this change, and its support was merged in OVS with this change in the 3.1 version:

    # ovs-vsctl get interface vhost0 statistics | sed -e 's#[{}]##g' -e 's#, #\n#g' | grep packets= | grep -v '=0$'
    rx_65_to_127_packets=2987595
    rx_packets=2987595
    rx_q0_good_packets=2987595
    rx_q0_size_65_127_packets=2987595
    tx_65_to_127_packets=14075727
    tx_packets=14075727
    tx_q0_good_packets=14075727
    tx_q0_size_65_127_packets=14075727

    More vhost-user statistics

    As a bonus of the work exposing per queue statistics, the vhost-user library started exposing other internal counters.

    The virtio driver (e.g., the Linux kernel driver by default) plugged on a vhost-user port may require guest notifications for signaling packets delivery. Triggering those notifications impacts the processing cost of such packets, which is why keeping track of the amount of notifications is of interest.

    Previously, OVS was exposing a coverage counter for those notifications, and until OVS 3.0, you could use the following:

    # ovs-appctl coverage/show | grep vhost_notification
    vhost_notification         0.0/sec     0.000/sec        2.0283/sec   total: 7302

    This coverage counter was only hinting at some vhost-user ports used by an unidentified virtual machine.

    Starting OVS 3.1, the coverage counter has been removed in favor of per queue and per port statistics (DPDK change / OVS change):

    # ovs-vsctl get interface vhost0 statistics | sed -e 's#[{}]##g' -e 's#, #\n#g' | grep guest_notifications
    rx_q0_guest_notifications=12
    rx_q1_guest_notifications=1
    tx_q0_guest_notifications=3
    tx_q1_guest_notifications=2

    This nice addition makes it possible to directly point at which virtual machine is slowing down packet processing. Other vhost-user statistics have been added, like exposing the vhost-user IOTLB cache internals. More may be added in the future as members of the community express new requirements.

    A final note about statistics

    As OVS stores per interface statistics in its ovsdb, choices were made to select generic (iow not driver specific) statistics, and that helps in a majority of use cases.

    However, if you do not find the driver-specific statistics you're looking for, it is still possible for debugging to use the DPDK telemetry tool and retrieve all unfiltered port statistics as follows:

    # echo /ethdev/xstats,0 | dpdk-telemetry.py -f /var/run/openvswitch/dpdk/rte
    {
      "/ethdev/xstats": {
        "rx_good_packets": 5553474,
        "tx_good_packets": 39406658860,
        "rx_good_bytes": 710844672,
        "tx_good_bytes": 4886425719104,
        "rx_missed_errors": 78892319,
        "rx_errors": 0,
        "tx_errors": 0,
        "rx_mbuf_allocation_errors": 0,
        "rx_q0_packets": 3705290,
        "rx_q0_bytes": 474277120,
        "rx_q0_errors": 0,
        "rx_q1_packets": 1848184,
        "rx_q1_bytes": 236567552,
        "rx_q1_errors": 0,
        "tx_q0_packets": 0,
        "tx_q0_bytes": 0,
        "tx_q1_packets": 3700615,
        "tx_q1_bytes": 458874621,
        "tx_q2_packets": 71,
        "tx_q2_bytes": 8120,
        "tx_q3_packets": 19696490435,
        "tx_q3_bytes": 2442364825811,
        "tx_q4_packets": 19706467739,
        "tx_q4_bytes": 2443602010552,
        "rx_wqe_errors": 0,
        "rx_unicast_packets": 84445793,
        "rx_unicast_bytes": 10471278332,
        "tx_unicast_packets": 39406658216,
        "tx_unicast_bytes": 4886425618784,
        "rx_multicast_packets": 0,
        "rx_multicast_bytes": 0,
        "tx_multicast_packets": 444,
        "tx_multicast_bytes": 35320,
        "rx_broadcast_packets": 0,
        "rx_broadcast_bytes": 0,
        "tx_broadcast_packets": 200,
        "tx_broadcast_bytes": 65000,
        "tx_phy_packets": 39406658860,
        "rx_phy_packets": 84445793,
        "rx_phy_crc_errors": 0,
        "tx_phy_bytes": 5044052354544,
        "rx_phy_bytes": 10809061504,
        "rx_phy_in_range_len_errors": 0,
        "rx_phy_symbol_errors": 0,
        "rx_phy_discard_packets": 0,
        "tx_phy_discard_packets": 0,
        "tx_phy_errors": 0,
        "rx_out_of_buffer": 78892319,
        "tx_pp_missed_interrupt_errors": 0,
        "tx_pp_rearm_queue_errors": 0,
        "tx_pp_clock_queue_errors": 0,
        "tx_pp_timestamp_past_errors": 0,
        "tx_pp_timestamp_future_errors": 0,
        "tx_pp_jitter": 0,
        "tx_pp_wander": 0,
        "tx_pp_sync_lost": 0
      }
    }

    Related Posts

    • Debugging Memory Issues with Open vSwitch DPDK

    • Non-root Open vSwitch in RHEL

    • Speeding up Open vSwitch with partial hardware offloading

    • The need for speed and the kernel datapath - recent improvements in UDP packets processing

    Recent Posts

    • More Essential AI tutorials for Node.js Developers

    • How to run a fraud detection AI model on RHEL CVMs

    • How we use software provenance at Red Hat

    • Alternatives to creating bootc images from scratch

    • How to update OpenStack Services on OpenShift

    What’s up next?

    GitOps has become a standard in deploying applications to Kubernetes, and many companies are adopting the methodology for their DevOps and cloud-native strategy. Download the GitOps Cookbook for useful recipes and examples for successful hands-on applications development and deployment with GitOps.

    Download the GitOps Cookbook
    Red Hat Developers logo LinkedIn YouTube Twitter Facebook

    Products

    • Red Hat Enterprise Linux
    • Red Hat OpenShift
    • Red Hat Ansible Automation Platform

    Build

    • Developer Sandbox
    • Developer Tools
    • Interactive Tutorials
    • API Catalog

    Quicklinks

    • Learning Resources
    • E-books
    • Cheat Sheets
    • Blog
    • Events
    • Newsletter

    Communicate

    • About us
    • Contact sales
    • Find a partner
    • Report a website issue
    • Site Status Dashboard
    • Report a security problem

    RED HAT DEVELOPER

    Build here. Go anywhere.

    We serve the builders. The problem solvers who create careers with code.

    Join us if you’re a developer, software engineer, web designer, front-end designer, UX designer, computer scientist, architect, tester, product manager, project manager or team lead.

    Sign me up

    Red Hat legal and privacy links

    • About Red Hat
    • Jobs
    • Events
    • Locations
    • Contact Red Hat
    • Red Hat Blog
    • Inclusion at Red Hat
    • Cool Stuff Store
    • Red Hat Summit

    Red Hat legal and privacy links

    • Privacy statement
    • Terms of use
    • All policies and guidelines
    • Digital accessibility

    Report a website issue