From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754931Ab2IXMGm (ORCPT ); Mon, 24 Sep 2012 08:06:42 -0400 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:56296 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753904Ab2IXMGl (ORCPT ); Mon, 24 Sep 2012 08:06:41 -0400 Message-ID: <50604BF0.1070607@linux.vnet.ibm.com> Date: Mon, 24 Sep 2012 17:32:56 +0530 From: Raghavendra K T Organization: IBM User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120216 Thunderbird/10.0.1 MIME-Version: 1.0 To: dlaor@redhat.com CC: Chegu Vinod , Peter Zijlstra , "H. Peter Anvin" , Marcelo Tosatti , Ingo Molnar , Avi Kivity , Rik van Riel , Srikar , "Nikunj A. Dadhania" , KVM , Jiannan Ouyang , "Andrew M. Theurer" , LKML , Srivatsa Vaddagiri , Gleb Natapov , Andrew Jones Subject: Re: [PATCH RFC 0/2] kvm: Improving undercommit,overcommit scenarios in PLE handler References: <20120921115942.27611.67488.sendpatchset@codeblue> <505C691D.4080801@hp.com> <505CA5BA.4020801@linux.vnet.ibm.com> <50601CE7.60801@redhat.com> In-Reply-To: <50601CE7.60801@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit x-cbid: 12092412-1396-0000-0000-000001EA3BDA Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/24/2012 02:12 PM, Dor Laor wrote: > In order to help PLE and pvticketlock converge I thought that a small > test code should be developed to test this in a predictable, > deterministic way. > > The idea is to have a guest kernel module that spawn a new thread each > time you write to a /sys/.... entry. > > Each such a thread spins over a spin lock. The specific spin lock is > also chosen by the /sys/ interface. Let's say we have an array of spin > locks *10 times the amount of vcpus. > > All the threads are running a > while (1) { > > spin_lock(my_lock); > sum += execute_dummy_cpu_computation(time); > spin_unlock(my_lock); > > if (sys_tells_thread_to_die()) break; > } > > print_result(sum); > > Instead of calling the kernel's spin_lock functions, clone them and make > the ticket lock order deterministic and known (like a linear walk of all > the threads trying to catch that lock). By Cloning you mean hierarchy of the locks? Also I believe time should be passed via sysfs / hardcoded for each type of lock we are mimicking > > This way you can easy calculate: > 1. the score of a single vcpu running a single thread > 2. the score of sum of all thread scores when #thread==#vcpu all > taking the same spin lock. The overall sum should be close as > possible to #1. > 3. Like #2 but #threads > #vcpus and other versions of #total vcpus > (belonging to all VMs) > #pcpus. > 4. Create #thread == #vcpus but let each thread have it's own spin > lock > 5. Like 4 + 2 > > Hopefully this way will allows you to judge and evaluate the exact > overhead of scheduling VMs and threads since you have the ideal result > in hand and you know what the threads are doing. > > My 2 cents, Dor > Thank you, I think this is an excellent idea. ( Though I am trying to put all the pieces together you mentioned). So overall we should be able to measure the performance of pvspinlock/PLE improvements with a deterministic load in guest. Only thing I am missing is, How to generate different combinations of the lock. Okay, let me see if I can come with a solid model for this.