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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 165A7C2D0CE for ; Fri, 24 Jan 2020 07:53:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DA7652071E for ; Fri, 24 Jan 2020 07:53:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="WE2DXd5V" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729431AbgAXHxY (ORCPT ); Fri, 24 Jan 2020 02:53:24 -0500 Received: from merlin.infradead.org ([205.233.59.134]:39454 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725817AbgAXHxX (ORCPT ); Fri, 24 Jan 2020 02:53:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=yuA59Cq86QbpEr2GrOS1my19i2Wm0DAniBfPEadru+E=; b=WE2DXd5VdOovwJVSYxSxfE6QZ n8413ndR5tjBKdTrfkMnM1yGlzr/9L1/JgTH7UQVY4LLbgWeYruwww37tzvLPwLtIE9vPisE2Yv4c DANqteyAoXxYNXLvTzGTavbTIzem6CUyASrfJ9n6t86d4eSHxE3WmmxVxMsHoHnSjzareP2xR3Qn9 fiLecZ8TgJvMBrimrxxWmNfEUXgpFK3FtGPOUR8zXXCleY8JD+iISEOLUgOw7pOdZa+01SK07b0oP VzZUunaCiW0otMSA818I140pkS8tKQVFzYpHEwLZ3ydHTofSySmjR0BuAwoxWFtszk4/eJZWVe1z5 X0FXVJN3w==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iutlf-0001Zl-48; Fri, 24 Jan 2020 07:52:39 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 4165F300677; Fri, 24 Jan 2020 08:50:55 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id AC2352B716B08; Fri, 24 Jan 2020 08:52:35 +0100 (CET) Date: Fri, 24 Jan 2020 08:52:35 +0100 From: Peter Zijlstra To: Alex Kogan Cc: Waiman Long , linux@armlinux.org.uk, Ingo Molnar , Will Deacon , Arnd Bergmann , linux-arch@vger.kernel.org, linux-arm-kernel , linux-kernel@vger.kernel.org, Thomas Gleixner , Borislav Petkov , hpa@zytor.com, x86@kernel.org, Hanjun Guo , Jan Glauber , Steven Sistare , Daniel Jordan , dave.dice@oracle.com Subject: Re: [PATCH v8 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Message-ID: <20200124075235.GX14914@hirez.programming.kicks-ass.net> References: <20191230194042.67789-1-alex.kogan@oracle.com> <20191230194042.67789-5-alex.kogan@oracle.com> <20200121132949.GL14914@hirez.programming.kicks-ass.net> <3862F8A1-FF9B-40AD-A88E-2C0BA7AF6F58@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3862F8A1-FF9B-40AD-A88E-2C0BA7AF6F58@oracle.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 23, 2020 at 04:33:54PM -0500, Alex Kogan wrote: > Let me put this question to you. What do you think the number should be? I think it would be very good to keep the inter-node latency below 1ms. But to realize that we need data on the lock hold times. Specifically for the heavily contended locks that make CNA worth it in the first place. I don't see that data, so I don't see how we can argue about this let alone call something reasonable.