Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754151AbbG0Rd5 (ORCPT ); Mon, 27 Jul 2015 13:33:57 -0400 Received: from g4t3427.houston.hp.com ([15.201.208.55]:59185 "EHLO g4t3427.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753637AbbG0Rd4 (ORCPT ); Mon, 27 Jul 2015 13:33:56 -0400 Message-ID: <55B66B81.1070508@hp.com> Date: Mon, 27 Jul 2015 13:33:53 -0400 From: Waiman Long User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130109 Thunderbird/10.0.12 MIME-Version: 1.0 To: Davidlohr Bueso CC: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Scott J Norton , Douglas Hatch Subject: Re: [PATCH v3 3/7] locking/pvqspinlock: Collect slowpath lock statistics References: <1437595962-21472-1-git-send-email-Waiman.Long@hp.com> <1437595962-21472-4-git-send-email-Waiman.Long@hp.com> <1437959674.25997.30.camel@stgolabs.net> In-Reply-To: <1437959674.25997.30.camel@stgolabs.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1234 Lines: 31 On 07/26/2015 09:14 PM, Davidlohr Bueso wrote: > On Wed, 2015-07-22 at 16:12 -0400, Waiman Long wrote: >> This patch enables the accumulation of kicking and waiting related >> PV qspinlock statistics when the new QUEUED_LOCK_STAT configuration >> option is selected. It also enables the collection of kicking and >> wakeup latencies which have a heavy dependency on the CPUs being used. >> >> The measured latencies for different CPUs are: >> >> CPU Wakeup Kicking >> --- ------ ------- >> Haswell-EX 89.8us 7.4us >> Westmere-EX 67.6us 9.3us >> > But you don't mention anything about the overhead of enabling > QUEUED_LOCK_STAT. This does several atomic ops, thus potentially > thrashing workloads. > Yes, QUEUED_LOCK_STAT will slow performance a bit. It is like enabling LOCK_STAT and you will expect some slow down too. It is essentially a debugging option to see what had actually happened in the system. It should be turned off in a production system. Cheers, Longman -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/