From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1C76AC433DB for ; Tue, 16 Feb 2021 10:23:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DBAF164DA8 for ; Tue, 16 Feb 2021 10:23:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229717AbhBPKW5 (ORCPT ); Tue, 16 Feb 2021 05:22:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54946 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230010AbhBPKV1 (ORCPT ); Tue, 16 Feb 2021 05:21:27 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 99D0EC061786; Tue, 16 Feb 2021 02:20:47 -0800 (PST) Date: Tue, 16 Feb 2021 11:20:44 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1613470846; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=7a6EbWhcc1He9imxspIn+eCQuB9DLKRDzdmRL5DBYhk=; b=k4Es/RI9TJqS8Whdcbr/nWxt7F9+yGDKNfzTIhTmEvi10ogJrC9YAwuAlPNqs31bwIrH+j n2yNtqOubFv7pCKUbcm4qCbP4z11nHgugLmKgkn+pomk6IquLT+LBnA3Z4di8kVovQmeM3 aybTjJ7bkYPnONMzRsB6ST9v57wwgrGAZJDlpqJ5d1Yt0RuL6pvquLtgeVlMxpA/EUVCLY kkdCbZh6gOqN2Ek6I+Ci5MXR2yPdnLBrhZ8/mWYxwvIZ0aaGgBLZ911xuQhFufuvKQfZ5W YGyB4aE3SxW/IOS/jOxH2daeEIrPYPOZexBJwOg1Vk9DrAPseT8RCxVUdMReDA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1613470846; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=7a6EbWhcc1He9imxspIn+eCQuB9DLKRDzdmRL5DBYhk=; b=sLsdW/5TPSKc5o1seFXs0fqEdHWJsS2WlIEPOV9yYyn1ourZEClZobFApUK1pqDqTBSnOK ZCjAsNHI4pGke8Bw== From: Sebastian Andrzej Siewior To: Peter Zijlstra Cc: =?utf-8?B?QW5kcsOp?= Almeida , Thomas Gleixner , Ingo Molnar , Darren Hart , linux-kernel@vger.kernel.org, Steven Rostedt , kernel@collabora.com, krisman@collabora.com, pgriffais@valvesoftware.com, z.figura12@gmail.com, joel@joelfernandes.org, malteskarupke@fastmail.fm, linux-api@vger.kernel.org, fweimer@redhat.com, libc-alpha@sourceware.org, linux-kselftest@vger.kernel.org, shuah@kernel.org, acme@kernel.org, corbet@lwn.net Subject: Re: [RFC PATCH 01/13] futex2: Implement wait and wake functions Message-ID: <20210216102044.e2cvvqdglqs23yfe@linutronix.de> References: <20210215152404.250281-1-andrealmeid@collabora.com> <20210215152404.250281-2-andrealmeid@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-02-16 10:56:14 [+0100], Peter Zijlstra wrote: > So while I'm in favour of adding a new interface, I'm not sure I see > benefit of reimplementing the basics, sure it seems simpler now, but > that's because you've not implemented all the 'fun' stuff. The last attempt tried to hide the updated interface within libc which did not fly. The global hash state is one of the problems because it leads to hash collisions of two unrelated locks. It will get simpler if we go into the kernel for each lock/unlock operation but this might not very good in terms of performance for locks which are mostly uncontended. I'm not sure how much we can cheat in terms of VDSO. Sebastian