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[209.85.208.47]) by smtp.gmail.com with ESMTPSA id wg1-20020a17090705c100b00a4e393b6349sm6627788ejb.5.2024.04.03.13.57.28 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Apr 2024 13:57:28 -0700 (PDT) Received: by mail-ed1-f47.google.com with SMTP id 4fb4d7f45d1cf-56829f41f81so367191a12.2 for ; Wed, 03 Apr 2024 13:57:28 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCVTfltx5n2LwsJXCY1yM/AprKHEPT14HR2J19AR6EONttcbal4WdZ75R3xM7PQj+tV0As2xP5AYPDawrwoqoYfeEFanJwDUeIGVaDTL X-Received: by 2002:a17:907:2d8f:b0:a4e:2ad3:60ff with SMTP id gt15-20020a1709072d8f00b00a4e2ad360ffmr339680ejc.47.1712177847931; Wed, 03 Apr 2024 13:57:27 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <969ccc0f-d909-4b45-908e-e98279777733@metaparadigm.com> <1a116a43-fd2e-4f03-8a17-75816fc62717@metaparadigm.com> In-Reply-To: <1a116a43-fd2e-4f03-8a17-75816fc62717@metaparadigm.com> From: Linus Torvalds Date: Wed, 3 Apr 2024 13:57:11 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: user-space concurrent pipe buffer scheduler interactions To: Michael Clark Cc: Jens Axboe , Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" On Wed, 3 Apr 2024 at 13:52, Michael Clark wrote: > > On 4/4/24 05:56, Linus Torvalds wrote: > > On Tue, 2 Apr 2024 at 13:54, Michael Clark wrote: > >> > >> I am working on a low latency cross-platform concurrent pipe buffer > >> using C11 threads and atomics. > > > > You will never get good performance doing spinlocks in user space > > unless you actually tell the scheduler about the spinlocks, and have > > some way to actually sleep on contention. > > > > Which I don't see you as having. > > We can work on this. It's been tried. Nobody ever found a use-case that is sufficiently convincing, but see the write-up at https://lwn.net/Articles/944895/ for a pointer to at least attempts. Linus