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[34.145.139.141]) by smtp.gmail.com with UTF8SMTPSA id af79cd13be357-7caf75d97d9sm210196485a.101.2025.05.07.13.43.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 May 2025 13:43:33 -0700 (PDT) Date: Wed, 07 May 2025 16:43:32 -0400 From: Willem de Bruijn To: Jon Kohler , ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, kuba@kernel.org, hawk@kernel.org, john.fastabend@gmail.com, netdev@vger.kernel.org, bpf@vger.kernel.org, jon@nutanix.com, aleksander.lobakin@intel.com, Willem de Bruijn , Jason Wang , Andrew Lunn , Eric Dumazet , Paolo Abeni , linux-kernel@vger.kernel.org (open list) Message-ID: <681bc5f4b261e_20dc6429482@willemb.c.googlers.com.notmuch> In-Reply-To: <20250506145530.2877229-2-jon@nutanix.com> References: <20250506145530.2877229-1-jon@nutanix.com> <20250506145530.2877229-2-jon@nutanix.com> Subject: Re: [PATCH net-next 1/4] tun: rcu_deference xdp_prog only once per batch Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Jon Kohler wrote: > Hoist rcu_dereference(tun->xdp_prog) out of tun_xdp_one, so that > rcu_deference is called once during batch processing. I'm skeptical that this does anything. The compiler can inline tun_xdp_one and indeed seems to do so. And then it can cache the read in a register if that is the best use of a register. > > No functional change intended. > > Signed-off-by: Jon Kohler