netdev - Re: [PATCH net-next v10 0/5] net: devmem: improve cpu cost of RX token management

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Message-ID: <aXhUfC7ZyYge1jti@mini-arch>
Date: Mon, 26 Jan 2026 22:00:28 -0800
From: Stanislav Fomichev <stfomichev@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Bobby Eshleman <bobbyeshleman@...il.com>,
	Mina Almasry <almasrymina@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Kuniyuki Iwashima <kuniyu@...gle.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	David Ahern <dsahern@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Jonathan Corbet <corbet@....net>,
	Andrew Lunn <andrew+netdev@...n.ch>, Shuah Khan <shuah@...nel.org>,
	Donald Hunter <donald.hunter@...il.com>,
	Stanislav Fomichev <sdf@...ichev.me>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
	asml.silence@...il.com, matttbe@...nel.org, skhawaja@...gle.com,
	Bobby Eshleman <bobbyeshleman@...a.com>
Subject: Re: [PATCH net-next v10 0/5] net: devmem: improve cpu cost of RX
 token management

On 01/26, Jakub Kicinski wrote:
> On Mon, 26 Jan 2026 10:45:22 -0800 Bobby Eshleman wrote:
> > I'm onboard with improving what we have since it helps all of us
> > currently using this API, though I'm not opposed to discussing a
> > redesign in another thread/RFC. I do see the attraction to locating the
> > core logic in one place and possibly reducing some complexity around
> > socket/binding relationships.
> > 
> > FWIW regarding nl, I do see it supports rtnl lock-free operations via
> > '62256f98f244 rtnetlink: add RTNL_FLAG_DOIT_UNLOCKED' and routing was
> > recently made lockless with that. I don't see / know of any fast path
> > precedent. I'm aware there are some things I'm not sure about being
> > relevant performance-wise, like hitting skb alloc an additional time
> > every release batch. I'd want to do some minimal latency comparisons
> > between that path and sockopt before diving head-first.
> 
> FTR I'm not really pushing Netlink specifically, it may work it 
> may not. Perhaps some other ioctl-y thing exists. Just in general
> setsockopt() on a specific socket feels increasingly awkward for 
> buffer flow. Maybe y'all disagree.
> 
> I thought I'd clarify since I may be seen as "Mr Netlink Everywhere" :)

>From my side, if we do a completely new uapi, my preference would be on
an af_xdp like mapped rings (presumably on a netlink socket?) to completely
avoid the user-kernel copies.