[ovs-dev] [PATCH v6 0/2] dpif-netlink: distribute polling to discreet handlers

Mark Gray mark.d.gray at redhat.com
Mon Sep 7 08:37:53 UTC 2020

Currently, the channel handlers are polled globally.  On some
systems, this causes a thundering herd issue where multiple
handler threads become active, only to do no work and immediately

The approach here is to push the netlink socket channels to discreet
handler threads to process, rather than polling on every thread.
This will eliminate the need to wake multiple threads.

To check:

  ip netns add left
  ip netns add right
  ip link add center-left type veth peer name left0 netns left
  ip link add center-right type veth peer name right0 netns right
  ip link set center-left up
  ip link set center-right up
  ip -n left ip link set left0 up
  ip -n left ip addr add dev left0
  ip -n right ip link set right0 up
  ip -n right ip addr add dev right0

  ovs-vsctl add-br br0
  ovs-vsctl add-port br0 center-right
  ovs-vsctl add-port br0 center-left

  # in one terminal
  perf record -e sched:sched_wakeup,irq:softirq_entry -ag

  # in a separate terminal
  ip netns exec left arping -I left0 -c 1

  # in the perf terminal after exiting
  perf script

Look for the number of 'handler' threads which were made active.


v2: Oops - forgot to commit my whitespace cleanups.
v3: one port latency results as per Matteo's comments

      min/avg/max/mdev = 21.5/36.5/96.5/1.0 us
    With Patch:
      min/avg/max/mdev = 5.3/9.7/98.4/0.5 us 
v4: Oops - first email did not send
v5:   min/avg/max/mdev = 9.3/10.4/33.6/2.2 us
v6: Split out the AUTHORS patch and added a cover letter as
    per Ilya's suggestion.
    Fixed 0-day issues.

Aaron Conole (1):
  dpif-netlink: distribute polling to discreet handlers

Mark Gray (1):
  id-pool: Add interface to check if id has been allocated

 lib/dpif-netlink.c | 320 +++++++++++++++++++++++++--------------------
 lib/id-pool.c      |  10 ++
 lib/id-pool.h      |   1 +
 3 files changed, 189 insertions(+), 142 deletions(-)


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