[dpdk-dev] [PATCH v2 0/5] vhost/virtio performance loopback utility

Zhihong Wang zhihong.wang at intel.com
Wed Jun 1 05:27:38 CEST 2016

This patch enables vhost/virtio pmd performance loopback test in testpmd.
All the features are for general usage.

The loopback test focuses on the maximum full-path packet forwarding
performance between host and guest, it runs vhost/virtio pmd only without
introducing extra overhead.

Therefore, the main requirement is traffic generation, since there's no
other packet generators like IXIA to help.

In current testpmd, iofwd is the best candidate to perform this loopback
test because it's the fastest possible forwarding engine: Start testpmd
iofwd in host with 1 vhost port, and start testpmd iofwd in the connected
guest with 1 corresponding virtio port, and these 2 ports form a forwarding
loop: Host vhost tx -> Guest virtio rx -> Guest virtio tx -> Host vhost rx.

As to traffic generation, "start tx_first" injects a burst of packets into
the loop.

However 2 issues remain:

   1. If only 1 burst of packets are injected in the loop, there will
      definitely be empty rx operations, e.g. When guest virtio port send
      burst to the host, then it starts the rx immediately, it's likely
      the packets are still being forwarded by host vhost port and haven't
      reached the guest yet.

      We need to fill up the ring to keep all pmds busy.

   2. iofwd doesn't provide retry mechanism, so if packet loss occurs,
      there won't be a full burst in the loop.

To address these issues, this patch:

   1. Add retry option in testpmd to prevent most packet losses.

   2. Add parameter to enable configurable tx_first burst number.

Other related improvements include:

   1. Handle all rxqs when multiqueue is enabled: Current testpmd forces a
      single core for each rxq which causes inconvenience and confusion.

      This change doesn't break anything, we can still force a single core
      for each rxq, by giving the same number of cores with the number of

      One example: One Red Hat engineer was doing multiqueue test, there're
      2 ports in guest each with 4 queues, and testpmd was used as the
      forwarding engine in guest, as usual he used 1 core for forwarding, as
      a results he only saw traffic from port 0 queue 0 to port 1 queue 0,
      then a lot of emails and quite some time are spent to root cause it,
      and of course it's caused by this unreasonable testpmd behavior.

      Moreover, even if we understand this behavior, if we want to test the
      above case, we still need 8 cores for a single guest to poll all the
      rxqs, obviously this is too expensive.

      We met quite a lot cases like this.

   2. Show topology at forwarding start: "show config fwd" also does this,
      but show it directly can reduce the possibility of mis-configuration.

      Like the case above, if testpmd shows topology at forwarding start,
      then probably all those debugging efforts can be saved.

   3. Add throughput information in port statistics display for "show port
      stats (port_id|all)".

Finally there's documentation update.

Example on how to enable vhost/virtio performance loopback test:

   1. Start testpmd in host with 1 vhost port only.

   2. Start testpmd in guest with only 1 virtio port connected to the
      corresponding vhost port.

   3. "set fwd io retry" in testpmds in both host and guest.

   4. "start" in testpmd in guest.

   5. "start tx_first 16" in testpmd in host.

Then use "show port stats all" to monitor the performance.

Changes in v2:

   1. Add retry as an option for existing forwarding engines except rxonly.

   2. Minor code adjustment and more detailed patch description.

Zhihong Wang (5):
  testpmd: add retry option
  testpmd: configurable tx_first burst number
  testpmd: show throughput in port stats
  testpmd: handle all rxqs in rss setup
  testpmd: show topology at forwarding start

 app/test-pmd/Makefile                       |   1 -
 app/test-pmd/cmdline.c                      | 118 +++++++++++++++++++-
 app/test-pmd/config.c                       |  79 +++++++++++---
 app/test-pmd/csumonly.c                     |  12 ++
 app/test-pmd/flowgen.c                      |  12 ++
 app/test-pmd/icmpecho.c                     |  15 +++
 app/test-pmd/iofwd.c                        |  22 +++-
 app/test-pmd/macfwd-retry.c                 | 164 ----------------------------
 app/test-pmd/macfwd.c                       |  13 +++
 app/test-pmd/macswap.c                      |  12 ++
 app/test-pmd/testpmd.c                      |  13 ++-
 app/test-pmd/testpmd.h                      |  14 ++-
 app/test-pmd/txonly.c                       |  12 ++
 doc/guides/testpmd_app_ug/run_app.rst       |   1 -
 doc/guides/testpmd_app_ug/testpmd_funcs.rst |  16 +--
 15 files changed, 303 insertions(+), 201 deletions(-)
 delete mode 100644 app/test-pmd/macfwd-retry.c


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