From: Ralf Lici <ralf@mandelbit.com>
To: openvpn-devel@lists.sourceforge.net
Date: Thu, 17 Sep 2026 17:29:54 +0200
Message-ID: <cover.1789658051.git.ralf@mandelbit.com>
MIME-Version: 1.0
Subject: [Openvpn-devel] [PATCH ovpn net-next 0/2] ovpn: reduce
 reference-count contention
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Errors-To: openvpn-devel-bounces@lists.sourceforge.net

Hi,

Currently ovpn holds peer and key-slot references while packets are
being processed and until asynchronous crypto completes. With traffic
for one peer spread across CPUs, the shared kref cachelines therefore
become contended even though both objects are normally long-lived.

This series converts both references to percpu_ref while preserving their
existing RCU-delayed destruction. The individual patch messages describe
the memory cost and cache-to-cache measurements.

The test used one peer, one AES-128-GCM key and 32 TCP streams on a
32-logical-CPU Ryzen 9 9950X with a ConnectX-5 hairpin. The encrypted RX
flow used one source port and one receive queue, so only TX exercised CPU
fan-out. perf c2c showed that each shared reference cacheline disappeared
after its respective conversion.

Thanks,

Ralf Lici
Mandelbit Srl

---
Ralf Lici (2):
  ovpn: use percpu references for peers
  ovpn: use percpu references for key slots

 drivers/net/ovpn/crypto.c      | 14 +++++++-------
 drivers/net/ovpn/crypto.h      | 15 +++++++++++----
 drivers/net/ovpn/crypto_aead.c |  7 ++++++-
 drivers/net/ovpn/netlink.c     |  6 +++---
 drivers/net/ovpn/peer.c        | 32 ++++++++++++++++++++------------
 drivers/net/ovpn/peer.h        | 34 ++++++++++++++++++++++++++++++----
 6 files changed, 77 insertions(+), 31 deletions(-)


base-commit: b8e9e7d82e7eefd5d2d528469d94ec20e96b38c3
-- 
2.55.0


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