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 BE0A3C83F2C for ; Mon, 4 Sep 2023 15:10:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351376AbjIDPK0 (ORCPT ); Mon, 4 Sep 2023 11:10:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58212 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229854AbjIDPKZ (ORCPT ); Mon, 4 Sep 2023 11:10:25 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17758BD for ; Mon, 4 Sep 2023 08:10:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=DJJHJ+QymPIKxYSrYEByrV1EJIZ8oJGKczAbfnVY+xY=; b=qLGMBYEEmw96TWHhMfbl8ouiyV p+BJUoYsgPwRQqRCw/CqUtdDpkVAj/umLaRpAJ4En3BoCzVxrDbKR4wQnw70goUKcXBuvcegnqaVZ ZgNu+L6AlMMrgqTuAU0xUzXIPvDd4HnkLambqz+kpYgE5uw6SVEcz+bZ34YN484WVE/DM7aml0XA1 QA/0mXv64wdHUAV5x08yT7F7WogIw4PO36cqZvaXKELyUh4tUFMMGOM9QFOqsvyifQ/tEjJ2lsxQv ywKMhlwd/cbTUS118xx76Cneg83j61kr+IHvPE492WP8h+z5WhwFhCPJllPhUo59+3zaJga0HAtvr wOPcK1sw==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1qdBDM-00H9gc-Si; Mon, 04 Sep 2023 15:10:08 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 7892D3005B2; Mon, 4 Sep 2023 17:10:08 +0200 (CEST) Date: Mon, 4 Sep 2023 17:10:08 +0200 From: Peter Zijlstra To: Bongkyu Kim Cc: 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: <20230904151008.GA25717@noisy.programming.kicks-ass.net> References: <20230901010704.18493-1-bongkyu7.kim@samsung.com> <20230901010704.18493-2-bongkyu7.kim@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230901010704.18493-2-bongkyu7.kim@samsung.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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?