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Date: Mon, 8 Sep 2025 19:15:50 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Petr Machata <petrm@nvidia.com>
Cc: "David S. Miller" <davem@davemloft.net>, Eric Dumazet
 <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>,
 <netdev@vger.kernel.org>, Simon Horman <horms@kernel.org>, Nikolay
 Aleksandrov <razor@blackwall.org>, Ido Schimmel <idosch@nvidia.com>,
 <bridge@lists.linux.dev>, <mlxsw@nvidia.com>
Subject: Re: [PATCH net-next 02/10] net: bridge: BROPT_FDB_LOCAL_VLAN_0:
 Look up FDB on VLAN 0 on miss
Message-ID: <20250908191550.11beb208@kernel.org>
In-Reply-To: <8087475009dce360fb68d873b1ed9c80827da302.1757004393.git.petrm@nvidia.com>
References: <cover.1757004393.git.petrm@nvidia.com>
	<8087475009dce360fb68d873b1ed9c80827da302.1757004393.git.petrm@nvidia.com>
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On Thu, 4 Sep 2025 19:07:19 +0200 Petr Machata wrote:
>  		dst = br_fdb_find_rcu(br, eth_hdr(skb)->h_dest, vid);
> +		if (unlikely(!dst && vid &&
> +			     br_opt_get(br, BROPT_FDB_LOCAL_VLAN_0))) {

What does the assembly look like for this? I wonder if we're not better
off with:

	unlikely(!dst) && vid && br_opt..

Checking dst will be very fast here, and if we missed we're already 
on the slow path. So maybe we're better off moving the rest of the
condition out of the fast path, too?