netdev - [PATCH net-next 00/15] vxlan: Convert FDB table to rhashtable

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Message-ID: <20250415121143.345227-1-idosch@nvidia.com>
Date: Tue, 15 Apr 2025 15:11:28 +0300
From: Ido Schimmel <idosch@...dia.com>
To: <netdev@...r.kernel.org>
CC: <davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<edumazet@...gle.com>, <andrew+netdev@...n.ch>, <horms@...nel.org>,
	<petrm@...dia.com>, <razor@...ckwall.org>, Ido Schimmel <idosch@...dia.com>
Subject: [PATCH net-next 00/15] vxlan: Convert FDB table to rhashtable

The VXLAN driver currently stores FDB entries in a hash table with a
fixed number of buckets (256), resulting in reduced performance as the
number of entries grows. This patchset solves the issue by converting
the driver to use rhashtable which maintains a more or less constant
performance regardless of the number of entries.

Measured transmitted packets per second using a single pktgen thread
with varying number of entries when the transmitted packet always hits
the default entry (worst case):

Number of entries | Improvement
------------------|------------
1k                | +1.12%
4k                | +9.22%
16k               | +55%
64k               | +585%
256k              | +2460%

The first patches are preparations for the conversion in the last patch.
Specifically, the series is structured as follows:

Patch #1 adds RCU read-side critical sections in the Tx path when
accessing FDB entries. Targeting at net-next as I am not aware of any
issues due to this omission despite the code being structured that way
for a long time. Without it, traces will be generated when converting
FDB lookup to rhashtable_lookup().

Patch #2-#5 simplify the creation of the default FDB entry (all-zeroes).
Current code assumes that insertion into the hash table cannot fail,
which will no longer be true with rhashtable.

Patches #6-#10 add FDB entries to a linked list for entry traversal
instead of traversing over them using the fixed size hash table which is
removed in the last patch.

Patches #11-#12 add wrappers for FDB lookup that make it clear when each
should be used along with lockdep annotations. Needed as a preparation
for rhashtable_lookup() that must be called from an RCU read-side
critical section.

Patch #13 treats dst cache initialization errors as non-fatal. See more
info in the commit message. The current code happens to work because
insertion into the fixed size hash table is slow enough for the per-CPU
allocator to be able to create new chunks of per-CPU memory.

Patch #14 adds an FDB key structure that includes the MAC address and
source VNI. To be used as rhashtable key.

Patch #15 does the conversion to rhashtable.

Ido Schimmel (15):
  vxlan: Add RCU read-side critical sections in the Tx path
  vxlan: Simplify creation of default FDB entry
  vxlan: Insert FDB into hash table in vxlan_fdb_create()
  vxlan: Unsplit default FDB entry creation and notification
  vxlan: Relocate assignment of default remote device
  vxlan: Use a single lock to protect the FDB table
  vxlan: Add a linked list of FDB entries
  vxlan: Use linked list to traverse FDB entries
  vxlan: Convert FDB garbage collection to RCU
  vxlan: Convert FDB flushing to RCU
  vxlan: Rename FDB Tx lookup function
  vxlan: Create wrappers for FDB lookup
  vxlan: Do not treat dst cache initialization errors as fatal
  vxlan: Introduce FDB key structure
  vxlan: Convert FDB table to rhashtable

 drivers/net/vxlan/vxlan_core.c      | 542 ++++++++++++----------------
 drivers/net/vxlan/vxlan_private.h   |  11 +-
 drivers/net/vxlan/vxlan_vnifilter.c |   8 +-
 include/net/vxlan.h                 |   5 +-
 4 files changed, 248 insertions(+), 318 deletions(-)

-- 
2.49.0