[PATCH net-next 0/9] net: bridge: vlan: broadcast fwding path optimizations

[Nikolay Aleksandrov <razor@blackwall.org>]

Hi,
This patch-set is the first step to removing unnecessary VLAN hash lookups
from the bridge fast-path and also provides additional broadcast path
optimization by considering only the port-VLANs that actually participate
in the VLAN instead of all bridge ports. Combined these changes bring
considerable improvements[1] and open the path to do the same for the most
common fdb forwarding path. As expected the pathological cases have the
largest gain, e.g. if we have 1 client / VM facing port and 1 upstream port
only participating in a VLAN with many other bridge ports, we consider only
those 2 when broadcasting in that VLAN.

For up to 8 ports we only use the port-VLAN list as the array doesn't make
much of a difference and is unnecessary. Note that the array is rebuilt on
every member add or delete when >8 members, I tested that and could do
2000 VLAN add/delete with 64 port-VLAN members / sec on my test VM.
If it ever becomes a problem we can optimize it further, for the time
being I prefer it is simpler.

Patches 01-02: factor out flooding code into helpers that will be used
               later (no functional changes intended).
Patch 03: Cache the pvid VLAN entry directly so VLAN ingress can return
          it without a lookup while using the entry as the single source
          of VLAN state.
Patch 04: Introduces a VLAN's port-VLAN rcu list, used to build rcu array
          and as a fallback when flooding without array.
Patch 05: Consider only port-VLAN members when broadcasting, the first
          major optimization, especially in bridges with more ports.
Patch 06: Build RCU array of current port-VLAN members to be used for
          flooding when ports are > BR_VLAN_PORT_ARRAY_THRESHOLD (8).
Patch 07: Introduce a bridge forwarding dst structure used to pass around
          port and VLAN (later could be used for more state) enabling the
          next patch to remove VLAN lookups.
Patch 08: Use the port-VLAN carried in the forwarding destination to remove
          two redundant VLAN hash lookups in the fast-path when
          broadcasting. Same optimization will be made for the common fdb
          forwarding path in a following patch-set.
Patch 09: Avoid unnecessary VLAN hash lookups in the flood neigh
          suppression path.

Thanks,
 Nik

[1] Test measurements, also present in patch 08's commit message

  The series were tested in a two CPU VM with packet generation and bridge
  forwarding on separate pinned CPUs. The results are medians of seven runs
  with 300000 64b tagged broadcast packets.

                   Mpps                   br_flood TSC cycles/input
  VIDs Ports  before    after    gain   before  after  reduction
     1  8/2   1.209298  1.636580   35.3%     1444    845      41.5%
     1  8/4   0.843175  0.986541   17.0%     3036   2527      16.8%
     1  8/8   0.508857  0.559844   10.0%     5999   5465       8.9%
     1 32/2   0.893896  1.586532   77.5%     3013    841      72.1%
     1 32/16  0.250567  0.282339   12.7%    13670  11137      18.5%
     1 32/32  0.135351  0.148461    9.7%    25429  22320      12.2%
     1 64/2   0.555010  1.603776  189.0%     5001    837      83.3%
     1 64/32  0.123831  0.149639   20.8%    27674  22602      18.3%
     1 64/64  0.069122  0.076047   10.0%    51508  45138      12.4%
    64  8/2   1.044185  1.500468   43.7%     1528    851      44.3%
    64  8/4   0.802680  0.977700   21.8%     3178   2546      19.9%
    64  8/8   0.479748  0.555419   15.8%     6283   5635      10.3%
    64 32/2   0.861074  1.561266   81.3%     3063    849      72.3%
    64 32/16  0.234011  0.280027   19.7%    14332  11165      22.1%
    64 32/32  0.126145  0.148085   17.4%    27225  22613      16.9%
    64 64/2   0.530587  1.496179  182.0%     4377    826      81.1%
    64 64/32  0.121105  0.147943   22.2%    29286  22541      23.0%
    64 64/64  0.063626  0.077051   21.1%    56147  45520      18.9%
  1024  8/2   1.008693  1.358408   34.7%     1538    879      42.8%
  1024  8/4   0.785636  0.943545   20.1%     3280   2704      17.6%
  1024  8/8   0.448194  0.521765   16.4%     6678   6011      10.0%
  1024 32/2   0.840864  1.417311   68.6%     2756    859      68.8%
  1024 32/16  0.195786  0.247129   26.2%    16269  12639      22.3%
  1024 32/32  0.097978  0.122742   25.3%    35249  29273      17.0%
  1024 64/2   0.536947  1.400985  160.9%     4421    849      80.8%
  1024 64/32  0.093962  0.123383   31.3%    37425  29197      22.0%
  1024 64/64  0.045147  0.057867   28.2%    72626  59198      18.5%


Nikolay Aleksandrov (9):
  net: bridge: factor out common flood completion handling
  net: bridge: factor out port flooding
  net: bridge: vlan: cache the pvid vlan entry directly
  net: bridge: vlan: introduce a list of port-VLANs in the master VLAN
  net: bridge: consider only port-VLAN members when flooding
  net: bridge: vlan: use an RCU array for large flood sets
  net: bridge: introduce a forwarding destination structure
  net: bridge: avoid egress VLAN lookups when flooding
  net: bridge: avoid VLAN lookups for flood neighbour suppression

 net/bridge/br_arp_nd_proxy.c |  51 ++++---
 net/bridge/br_device.c       |   8 +-
 net/bridge/br_forward.c      | 272 ++++++++++++++++++++++-------------
 net/bridge/br_input.c        |   4 +-
 net/bridge/br_mst.c          |  13 +-
 net/bridge/br_private.h      |  59 +++++---
 net/bridge/br_vlan.c         | 155 ++++++++++++--------
 net/bridge/br_vlan_options.c |  12 +-
 8 files changed, 347 insertions(+), 227 deletions(-)

-- 
2.47.3