From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH v8 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Date: Fri, 24 Jan 2020 08:52:35 +0100 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-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <3862F8A1-FF9B-40AD-A88E-2C0BA7AF6F58@oracle.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane-mx.org@lists.infradead.org To: Alex Kogan Cc: linux-arch@vger.kernel.org, Hanjun Guo , Arnd Bergmann , dave.dice@oracle.com, Jan Glauber , x86@kernel.org, Will Deacon , linux@armlinux.org.uk, Steven Sistare , linux-kernel@vger.kernel.org, Ingo Molnar , Borislav Petkov , hpa@zytor.com, Waiman Long , Thomas Gleixner , Daniel Jordan , linux-arm-kernel List-Id: linux-arch.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. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 Date: Fri, 24 Jan 2020 08:52:35 +0100 From: Peter Zijlstra 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> Sender: linux-arch-owner@vger.kernel.org List-ID: 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 Message-ID: <20200124075235.oaetb2bEaqB_ezSxnCHzBVIKQQ3e9CBk4pGB5_Ns53E@z> 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.