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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) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: u5ktej818qbe4ekfbdi8fwd9bob8rdx4 X-Rspamd-Queue-Id: 0EBA1140004 X-HE-Tag: 1781085343-201483 X-HE-Meta: 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 cn91dghn 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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,