[ovs-dev] [PATCH v4 00/12] Reconfigure netdev at runtime

[Daniele Di Proietto]

Currently we treat set_multiq() calls specially in netdev and dpif-netdev:
every pmd thread must be stopped and set_multiq() is allowed to destroy and
recreate the device.

I think we can improve this by:
* Generalizing the mechanism to allow changing other parameters at runtime
  (such as MTU).
* Involving less the above layer (dpif-netdev).  The request for changes
  often comes from below (netdev_dpdk_set_config(), or the vhost new_device()
  callback).  There's no need for dpif-netdev to remember the requested value,
  all that it needs to know is that a configuration change is requested.

This series implements exactly this: a mechanism to allow a netdev provider
to request configuration changes, to which dpif-netdev will respond by
stopping rx/tx and calling a netdev function to appy the new configuration.

The new mechanism is used in this series to replace the set_multiq() call,
but the idea is to use it also at least for:

* Changing the MTU at runtime
* Automatically detecting the number of rx queues for a vhost-user device

The first commits also clean up some code in dpif-netdev and make the ports
cmap fully RCU protected.

v4:
* Added another patch to uniform names of variables in netdev-dpdk (no
  functional change)
* Update some netdev comments to document the relation between
  netdev_set_multiq() and netdev_reconfigure()
* Clarify that when netdev_reconfigure() is called no call to netdev_send()
  or netdev_rxq_recv() must be issued.
* Move check to skip reconfiguration in netdev_dpdk_reconfigure() before
  rte_eth_dev_stop().

v3:
* Fixed another outdated comment about rx queue configuration, as pointed out
  by Mark
* Removed unnecessary and buggy initialization of requested_n_rxq in
  reconfigure_pmd_threads().
* Removed unused 'err' variable in netdev_dpdk_set_multiq().
* Changed comparison in netdev_set_multiq() to use previous
  'netdev->requested_n_txq' instead of 'netdev->up.n_txq'
* Return immediately in netdev_dpdk_reconfigure() if configuration didn't
  change anything.

v2:
* Fixed do_add_port(): we have to call netdev_reconfigure() before opening
  the rxqs.  This prevents memory leaks, and makes sure that the datapath
  polls the appropriate number of queues
* Fixed netdev_dpdk_vhost_set_multiq(): it must call
  netdev_request_reconfigure(). Since it is now equal to
  netdev_dpdk_set_multiq(), the two function have been merged.
* Fixed netdev_dpdk_set_config(): dev->requested_n_rxq is now accessed
  while holding the appropriate mutex.
* Fixed some outdated comments about rx queue configuration.


Daniele Di Proietto (12):
  netdev-dpdk: Consistent variable naming.
  dpif-netdev: Proper error handling in do_add_port().
  dpif-netdev: Keep count of elements in port->rxq[].
  dpif-netdev: Do not keep refcount for ports.
  dpif-netdev: Remove useless dpif-dummy/delete-port appctl.
  dpif-netdev: Wait an RCU grace period before freeing ports.
  ofproto-dpif: Call dpif_poll_threads_set() before dpif_run()
  dpif-netdev: Change pmd thread configuration in dpif_netdev_run().
  dpif-netdev: Document locking discipline for non_pmd_mutex.
  dpif-netdev: Fix reconfigure_pmd_threads().
  netdev: Add reconfigure request mechanism.
  netdev-dpdk: Use ->reconfigure() call to change rx/tx queues.

 lib/dpif-netdev.c      | 435 +++++++++++++++++---------------
 lib/dpif-provider.h    |   3 +-
 lib/netdev-bsd.c       |   1 +
 lib/netdev-dpdk.c      | 654 +++++++++++++++++++++++++------------------------
 lib/netdev-dummy.c     |   1 +
 lib/netdev-linux.c     |   1 +
 lib/netdev-provider.h  |  50 ++--
 lib/netdev-vport.c     |   1 +
 lib/netdev.c           |  72 ++++--
 lib/netdev.h           |   7 +-
 ofproto/ofproto-dpif.c |   4 +-
 tests/bridge.at        |   4 +-
 12 files changed, 668 insertions(+), 565 deletions(-)

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2.1.4