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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E96C1C83F2C for ; Mon, 4 Sep 2023 19:11:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241296AbjIDTLo (ORCPT ); Mon, 4 Sep 2023 15:11:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43634 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233255AbjIDTLn (ORCPT ); Mon, 4 Sep 2023 15:11:43 -0400 Received: from mail-wm1-x333.google.com (mail-wm1-x333.google.com [IPv6:2a00:1450:4864:20::333]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0F6AE1707 for ; Mon, 4 Sep 2023 12:11:36 -0700 (PDT) Received: by mail-wm1-x333.google.com with SMTP id 5b1f17b1804b1-40037db2fe7so18049405e9.0 for ; Mon, 04 Sep 2023 12:11:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1693854694; x=1694459494; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=N4f6P28VPyXCYBikWvlnwCAAUPktzMnywAo5GqC9gYk=; b=ggGMbjTBCT99RhrkHVkqJWYgLBVgAayemTAVhTCeQHHPl/gqib9nKFjduvpXyUnRzR Vm/Bhl6RARHGQEtuZa0UxtTCVNhQJtSbs9/uA4+0EvUIOmpWANKwY2MeRo6gADQCtvNr R7PjjS+ozKvRlZuVoPCU+OvmVgOxFSyuG3zTkLT779zwVtlmfLnGyzYe8tRqxl0J4tMp BLCEnHvnl2mrJC5f4oZwKyJvFPnrnhnt3+gR1Eqx6XnnGCcMhjv1q63gqm0WM3BJbkbi GbxdV9gKkAJa5ZSSjGiea+FShd1GRncTD2zf3KVbvmSzxEnf15jV6eUAacaG+XcW6SkF ppmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1693854694; x=1694459494; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=N4f6P28VPyXCYBikWvlnwCAAUPktzMnywAo5GqC9gYk=; b=hfHjiAKmEcOzmEfK1ezRw0b4paA1jf8WUK3a2eP8dZXOHaXddIBklANdXrlSkkr7T9 C+x9Eirrl7dyk+nSHc1v2py0jW0vR/Ly99Rfg1KxRPcbob7e2ac5wGfej93RnHSz7zeK O8nlIKV8It1D7K16dbRJydy3wfNWXc5iFYm5NcShIfpE+04o2W/onX15svX0DyUzd5RC ilIYNkGEd/RUT0UPlqsS2g6motCeDEXHfqU2bK44J+NGqrUL6ij6Jm0mM38+P57Q6Xox Qf2k9ptwoxhjfjemihZFaLC5WT3vGFpn5tVTfP0fA6xId8Lu5M09dsfhSDOgeJ2Ajg/K rl1A== X-Gm-Message-State: AOJu0YwvDex5W+Wsym0YuthyFvZBAgzQS7V1zLtwfsuGtc5sqMJnv0+e L6bBw8/Ej5mtwQp0mD1p0Yk= X-Google-Smtp-Source: AGHT+IGf7CWEVAyMN78Enrsi6jocXZ2nX2wgaHVClC5M6lxqpSPdyOyE6kV0KAKOXi3GZmpf4uQEVg== X-Received: by 2002:a5d:6142:0:b0:317:6cd2:b90c with SMTP id y2-20020a5d6142000000b003176cd2b90cmr8808958wrt.13.1693854694332; Mon, 04 Sep 2023 12:11:34 -0700 (PDT) Received: from gmail.com (1F2EF6A2.nat.pool.telekom.hu. [31.46.246.162]) by smtp.gmail.com with ESMTPSA id l10-20020a5d4bca000000b003180155493esm15228687wrt.67.2023.09.04.12.11.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Sep 2023 12:11:33 -0700 (PDT) Sender: Ingo Molnar Date: Mon, 4 Sep 2023 21:11:31 +0200 From: Ingo Molnar To: Peter Zijlstra Cc: Bongkyu Kim , mingo@redhat.com, will@kernel.org, longman@redhat.com, boqun.feng@gmail.com, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org Subject: Re: [PATCH v2 1/2] Revert "locking/rwsem: Remove reader optimistic spinning" Message-ID: References: <20230901010704.18493-1-bongkyu7.kim@samsung.com> <20230901010704.18493-2-bongkyu7.kim@samsung.com> <20230904151008.GA25717@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230904151008.GA25717@noisy.programming.kicks-ass.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra wrote: > On Fri, Sep 01, 2023 at 10:07:03AM +0900, Bongkyu Kim wrote: > > This reverts commit 617f3ef95177840c77f59c2aec1029d27d5547d6. > > > > In mobile environment, reader optimistic spinning is still useful > > because there're not many readers. In my test result at android device, > > it improves application startup time about 3.8% > > App startup time is most important factor for android user expriences. > > So, re-enable reader optimistic spinning by this commit. And, > > the later patch will make it optional feature by cmdline. > > I'm not seeing any mention on how this interacts with all the rwsem work > that has been done since that commit, like the handoff rework. > > Why is a straight revert a sane thing at this point? Yeah, so this should probably be titled: locking/rwsem: Reintroduce reader optimistic spinning ... instead of the double-negative 'remove removal' thing that is indeed confusing. Thanks, Ingo