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Date: Fri, 4 Sep 2026 15:11:46 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Bobby Eshleman <bobbyeshleman@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>, Neal Cardwell
 <ncardwell@google.com>, Kuniyuki Iwashima <kuniyu@google.com>, "David S.
 Miller" <davem@davemloft.net>, Paolo Abeni <pabeni@redhat.com>, Simon
 Horman <horms@kernel.org>, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org, Stanislav Fomichev <sdf@fomichev.me>, Mina
 Almasry <almasrymina@google.com>, David Wei <dw@davidwei.uk>, Bobby
 Eshleman <bobbyeshleman@meta.com>
Subject: Re: [PATCH net-next] tcp: devmem: only pre-allocate tokens the
 receiver can consume
Message-ID: <20260904151146.602c61a4@kernel.org>
In-Reply-To: <20260902-b4-net-next_devmem-token-refill-v1-1-81d8990e5e17@meta.com>
References: <20260902-b4-net-next_devmem-token-refill-v1-1-81d8990e5e17@meta.com>
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On Wed, 02 Sep 2026 15:24:19 -0700 Bobby Eshleman wrote:
> Testing on a CX7 w/ GRO and a steady sendmsg() flow of 1MB per send, we
> see a typical RX-side skb touch upwards of ~32KB. With a 4KB recvmsg
> size, probing shows that ~75% of the allocated tokens are not used.

4kB seems unreasonably small. Is there a real life reason to use such
a small buffer / read length?