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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-490be1f69bcsm591850845e9.8.2026.06.10.02.55.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Jun 2026 02:55:41 -0700 (PDT) Date: Wed, 10 Jun 2026 10:55:40 +0100 From: David Laight To: Herbert Xu Cc: Linus Torvalds , luto@amacapital.net, safinaskar@gmail.com, 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: <20260610105540.5901a5be@pumpkin> In-Reply-To: References: X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) 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=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 10 Jun 2026 13:09:19 +0800 Herbert Xu wrote: > Linus Torvalds wrote: > > > > Because I think splice() is a *cool* feature. It was always *clever*. > > I just don't think it's worth the pain it has cause. > > > > And it's been around for a long long time, and after more than two > > decades it's still most definitely not _widely_ used. > > A couple of years ago I used tee(2) in dash(1) so that we could > avoid reading the input line byte-by-byte which is what every other > shell does in order to pass the rest of stdin to the executed > command. The shell just needs something like MSG_PEEK to do a non-consuming read from a pipe. (Without the strange behaviour of a second offset.) That would be simple and could have been implemented 40 years ago. -- David > > https://git.kernel.org/pub/scm/utils/dash/dash.git/commit/?id=44b15ea09a9ee5872cf477e4ffc6b42ef37d1e46 > > It's definitely niche but made a huge performance difference to > this rather common scenario: > > echo 'command > ... > rest of stdin' | sh > > I didn't even know tee(2) prior to this, even though it was added > way back. > > Thanks,