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Date: Fri, 27 Mar 2026 20:29:58 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Dimitri Daskalakis <dimitri.daskalakis1@gmail.com>
Cc: "David S . Miller" <davem@davemloft.net>, Alexander Duyck
 <alexanderduyck@fb.com>, Eric Dumazet <edumazet@google.com>, Paolo Abeni
 <pabeni@redhat.com>, Andrew Lunn <andrew+netdev@lunn.ch>, Simon Horman
 <horms@kernel.org>, Mike Marciniszyn <mike.marciniszyn@gmail.com>, Lee
 Trager <lee@trager.us>, Jacob Keller <jacob.e.keller@intel.com>, Mohsin
 Bashir <mohsin.bashr@gmail.com>, Mina Almasry <almasrymina@google.com>,
 netdev@vger.kernel.org, kernel-team@meta.com
Subject: Re: [PATCH net 0/2] Fix page fragment handling when PAGE_SIZE > 4K
Message-ID: <20260327202958.53d26d46@kernel.org>
In-Reply-To: <20260324195123.3486219-1-dimitri.daskalakis1@gmail.com>
References: <20260324195123.3486219-1-dimitri.daskalakis1@gmail.com>
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On Tue, 24 Mar 2026 12:51:21 -0700 Dimitri Daskalakis wrote:
> FBNIC operates on fixed size descriptors (4K). When the OS supports pages
> larger than 4K, we fragment the page across multiple descriptors.
> 
> While performance testing, I found several issues with our page fragment
> handling, resulting in low throughput and potential RX stalls.

Google AI reviewer points out that we will also be toast if someone
configures the ring size to just 16 descriptors. Can you check what
is the min size that doesn't wedge w/ 64kB pages and let's just set
the min to that instead of the current 16?