netdev - [PATCH net-next 0/4] inetpeer: reduce false sharing and atomic operations

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Message-ID: <20241213130212.1783302-1-edumazet@google.com>
Date: Fri, 13 Dec 2024 13:02:08 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, Simon Horman <horms@...nel.org>, 
	David Ahern <dsahern@...nel.org>, Kuniyuki Iwashima <kuniyu@...zon.com>, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 0/4] inetpeer: reduce false sharing and atomic operations

After commit 8c2bd38b95f7 ("icmp: change the order of rate limits"),
there is a risk that a host receiving packets from an unique
source targeting closed ports is using a common inet_peer structure
from many cpus.

All these cpus have to acquire/release a refcount and update
the inet_peer timestamp (p->dtime)

Switch to pure RCU to avoid changing the refcount, and update
p->dtime only once per jiffy.

Tested:
  DUT : 128 cores, 32 hw rx queues.
  receiving 8,400,000 UDP packets per second, targeting closed ports.

Before the series:
- napi poll can not keep up, NIC drops 1,200,000 packets
  per second. 
- We use 20 % of cpu cycles

After this series:
- All packets are received (no more hw drops)
- We use 12 % of cpu cycles.

Eric Dumazet (4):
  inetpeer: remove create argument of inet_getpeer_v[46]()
  inetpeer: remove create argument of inet_getpeer()
  inetpeer: update inetpeer timestamp in inet_getpeer()
  inetpeer: do not get a refcount in inet_getpeer()

 include/net/inetpeer.h | 12 +++++-------
 net/ipv4/icmp.c        |  6 +++---
 net/ipv4/inetpeer.c    | 29 ++++++++---------------------
 net/ipv4/ip_fragment.c | 15 ++++++++++-----
 net/ipv4/route.c       | 17 +++++++++--------
 net/ipv6/icmp.c        |  6 +++---
 net/ipv6/ip6_output.c  |  6 +++---
 net/ipv6/ndisc.c       |  8 +++++---
 8 files changed, 46 insertions(+), 53 deletions(-)

-- 
2.47.1.613.gc27f4b7a9f-goog