netdev - Re: [PATCH net-next 1/4] net: rps: change skb_flow

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Message-ID: <67f41f203509e_3a74d5294de@willemb.c.googlers.com.notmuch>
Date: Mon, 07 Apr 2025 14:53:20 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Eric Dumazet <edumazet@...gle.com>, 
 "David S . Miller" <davem@...emloft.net>, 
 Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, 
 Willem de Bruijn <willemb@...gle.com>, 
 netdev@...r.kernel.org, 
 eric.dumazet@...il.com, 
 Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next 1/4] net: rps: change skb_flow_limit() hash
 function

Eric Dumazet wrote:
> As explained in commit f3483c8e1da6 ("net: rfs: hash function change"),
> masking low order bits of skb_get_hash(skb) has low entropy.
> 
> A NIC with 32 RX queues uses the 5 low order bits of rss key
> to select a queue. This means all packets landing to a given
> queue share the same 5 low order bits.
> 
> Switch to hash_32() to reduce hash collisions.
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Reviewed-by: Willem de Bruijn <willemb@...gle.com>