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Date: Wed, 17 Jul 2024 07:12:18 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Paolo Abeni <pabeni@redhat.com>
Cc: davem@davemloft.net, netdev@vger.kernel.org, edumazet@google.com,
 alexanderduyck@fb.com, kernel-team@meta.com
Subject: Re: [PATCH net] eth: fbnic: don't build the driver when skb has
 more than 25 frags
Message-ID: <20240717071218.72ec1bc6@kernel.org>
In-Reply-To: <43bc03f0-5e5a-4265-898b-8ca526d6cc75@redhat.com>
References: <20240717133744.1239356-1-kuba@kernel.org>
	<43bc03f0-5e5a-4265-898b-8ca526d6cc75@redhat.com>
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On Wed, 17 Jul 2024 15:44:09 +0200 Paolo Abeni wrote:
> I think that with aarch MAX_SKB_FRAGS should be max 21. Aarch cacheline 
> size is 128, right? The frag independent part of skb_shared_info takes 
> 48 bytes, and sizeof(skb_frag_t) == 16:
> 
> (512 - 128 - 48)/16 = 21

Hm, my grep foo must be low, I don't see aarch64 with 128B cache lines.
But I do see powerpc, so we can stick to 21 to be safe.