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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4601f2dcae2sm35545066f8f.6.2026.06.06.03.22.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 06 Jun 2026 03:22:53 -0700 (PDT) Date: Sat, 6 Jun 2026 11:22:52 +0100 From: David Laight To: Stefan Metzmacher Cc: Linus Torvalds , Andy Lutomirski , Askar Safin , akpm@linux-foundation.org, axboe@kernel.dk, brauner@kernel.org, david@kernel.org, dhowells@redhat.com, hch@infradead.org, jack@suse.cz, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, miklos@szeredi.hu, netdev@vger.kernel.org, patches@lists.linux.dev, pfalcato@suse.de, viro@zeniv.linux.org.uk, willy@infradead.org Subject: Re: [PATCH 0/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2 Message-ID: <20260606112252.3c70bad6@pumpkin> In-Reply-To: <634c8ae2-3f1c-46b1-b002-1e2ac797dd80@samba.org> References: <20260602225426.122258-1-safinaskar@gmail.com> <512d948f-7883-4d8c-b2c5-a777e70ca975@samba.org> <20260605131942.4584728e@pumpkin> <634c8ae2-3f1c-46b1-b002-1e2ac797dd80@samba.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 5 Jun 2026 17:20:34 +0200 Stefan Metzmacher wrote: > Hi David, > > >>> So sendfile() as a concept (whether you use combinations of splice() > >>> system calls or the sendfile system call itsefl) isn't necessarily > >>> only about the zero-copy, it's really also about avoiding the user > >>> space memory management. > >> > >> I don't think so. Ok, maybe for webservers just serving tiny > >> html files, that's true. But for me with Samba it's really the > >> copy_to/from_iter() that is the major factor. > > > > Is that copy also doing the ip checksum? > > Not in my tests. I guess there's offload in the network hardware > for this. There will be, it is just whether the syscall checksum is actually being suppressed. -- David > > At least at the syscall layer of sendmsg() there's no checksuming > happening. > > metze >