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Date: Wed, 6 Dec 2023 08:03:33 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Jesper Dangaard Brouer <hawk@kernel.org>
Cc: Lorenzo Bianconi <lorenzo@kernel.org>, aleksander.lobakin@intel.com,
 netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com,
 pabeni@redhat.com, lorenzo.bianconi@redhat.com, bpf@vger.kernel.org,
 toke@redhat.com, willemdebruijn.kernel@gmail.com, jasowang@redhat.com,
 sdf@google.com
Subject: Re: [PATCH v3 net-next 2/2] xdp: add multi-buff support for xdp
 running in generic mode
Message-ID: <20231206080333.0aa23754@kernel.org>
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On Wed, 6 Dec 2023 13:41:49 +0100 Jesper Dangaard Brouer wrote:
> BUT then I realized that PP have a weakness, which is the return/free
> path that need to take a normal spin_lock, as that can be called from
> any CPU (unlike the RX/alloc case).  Thus, I fear that making multiple
> devices share a page_pool via softnet_data, increase the chance of lock
> contention when packets are "freed" returned/recycled.

I was thinking we can add a pcpu CPU ID to page pool so that
napi_pp_put_page() has a chance to realize that its on the "right CPU"
and feed the cache directly.