netdev - Re: [PATCH net-next v2 1/2] net: Make nexthop-dumps scale linearly with the number of nexthops

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Message-ID: <aKGV-OQ_EO749Xi0@shredder>
Date: Sun, 17 Aug 2025 11:42:32 +0300
From: Ido Schimmel <idosch@...sch.org>
To: cpaasch@...nai.com
Cc: David Ahern <dsahern@...nel.org>,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 1/2] net: Make nexthop-dumps scale linearly
 with the number of nexthops

On Sat, Aug 16, 2025 at 04:12:48PM -0700, Christoph Paasch via B4 Relay wrote:
> From: Christoph Paasch <cpaasch@...nai.com>
> 
> When we have a (very) large number of nexthops, they do not fit within a
> single message. rtm_dump_walk_nexthops() thus will be called repeatedly
> and ctx->idx is used to avoid dumping the same nexthops again.
> 
> The approach in which we avoid dumping the same nexthops is by basically
> walking the entire nexthop rb-tree from the left-most node until we find
> a node whose id is >= s_idx. That does not scale well.
> 
> Instead of this inefficient approach, rather go directly through the
> tree to the nexthop that should be dumped (the one whose nh_id >=
> s_idx). This allows us to find the relevant node in O(log(n)).

[...]

> Signed-off-by: Christoph Paasch <cpaasch@...nai.com>

Reviewed-by: Ido Schimmel <idosch@...dia.com>