[ovs-dev] [PATCH v4 0/4] Support dynamic rebalancing of offloaded flows

Sriharsha Basavapatna sriharsha.basavapatna at broadcom.com
Thu Jul 12 07:29:30 UTC 2018

With the current OVS offload design, when an offload-device fails to add a
flow rule and returns an error, OVS adds the rule to the kernel datapath.
The flow gets processed by the kernel datapath for the entire life of that
flow. This is fine when an error is returned by the device due to lack of
support for certain keys or actions.

But when an error is returned due to temporary conditions such as lack of
resources to add a flow rule, the flow continues to be processed by kernel
even when resources become available later. That is, those flows never get
offloaded again. This problem becomes more pronounced when a flow that has
been initially offloaded may have a smaller packet rate than a later flow
that could not be offloaded due to lack of resources. This leads to
inefficient use of HW resources and wastage of host CPU cycles.

This patch-set addresses this issue by providing a way to detect temporary
offload resource constraints (Out-Of-Resource or OOR condition) and to
selectively and dynamically offload flows with a higher packets-per-second
(pps) rate. This dynamic rebalancing is done periodically on netdevs that
are in OOR state until resources become available to offload all pending

The patch-set involves the following changes at a high level:

1. Detection of Out-Of-Resources (OOR) condition on an offload-capable 
2. Gathering flow offload selection criteria for all flows on an OOR netdev;
   i.e, packets-per-second (pps) rate of flows for offloaded and
   non-offloaded (pending) flows.
3. Dynamically replacing offloaded flows with a lower pps-rate, with
   non-offloaded flows with a higher pps-rate, on an OOR netdev. 
4. A new OpenvSwitch configuration option - "offload-rebalancing"
   to enable this policy.


  - Updated parse_flow_put() with the following changes:
    - Fixed outdev memory leak with multiple output actions
    - Moved variables closer to their first use
    - Removed outdev check while setting oor, since indev is sufficient

  - Removed some VLOG_DBG() in patches 2 and 3
  - Reworded a few VLOG_DBG() in patch 3
  - Fixed a comment line in patch 3

  - Fixed build errors reported by 0-day robot
  - Updated patch prefixes with relevant subsystem names


Sriharsha Basavapatna (4):
  dpif-netlink: Detect Out-Of-Resource condition on a netdev
  revalidator: Gather packets-per-second rate of flows
  revalidator: Rebalance offloaded flows based on the pps rate
  netdev: Add a configuration option to enable dynamic rebalancing of

 lib/dpif-netdev.c             |   3 +-
 lib/dpif-netlink.c            |  25 +-
 lib/dpif-provider.h           |   8 +-
 lib/dpif.c                    |  20 +-
 lib/dpif.h                    |  20 +-
 lib/flow.c                    |  27 ++
 lib/flow.h                    |   1 +
 lib/netdev-provider.h         |   8 +
 lib/netdev.c                  |  45 +++
 lib/netdev.h                  |   2 +
 ofproto/ofproto-dpif-upcall.c | 571 +++++++++++++++++++++++++++++++++-
 vswitchd/vswitch.xml          |  22 ++
 12 files changed, 732 insertions(+), 20 deletions(-)


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