From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mtagate1.de.ibm.com (mtagate1.de.ibm.com [195.212.17.161]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mtagate1.de.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id DB68CDE49E for ; Thu, 21 Aug 2008 23:31:55 +1000 (EST) Received: from d12nrmr1607.megacenter.de.ibm.com (d12nrmr1607.megacenter.de.ibm.com [9.149.167.49]) by mtagate1.de.ibm.com (8.13.1/8.13.1) with ESMTP id m7LDVmPD031594 for ; Thu, 21 Aug 2008 13:31:48 GMT Received: from d12av03.megacenter.de.ibm.com (d12av03.megacenter.de.ibm.com [9.149.165.213]) by d12nrmr1607.megacenter.de.ibm.com (8.13.8/8.13.8/NCO v9.0) with ESMTP id m7LDVmpt1663020 for ; Thu, 21 Aug 2008 15:31:48 +0200 Received: from d12av03.megacenter.de.ibm.com (loopback [127.0.0.1]) by d12av03.megacenter.de.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m7LDVldu026940 for ; Thu, 21 Aug 2008 15:31:48 +0200 Message-ID: <48AD6E42.6060406@linux.vnet.ibm.com> Date: Thu, 21 Aug 2008 15:31:46 +0200 From: Christian Ehrhardt MIME-Version: 1.0 To: Josh Boyer Subject: Re: [PATCH 4/4] kvmppc: convert wrteei to wrtee as kvm guest optimization References: <1219142204-12044-1-git-send-email-ehrhardt@linux.vnet.ibm.com> <1219142204-12044-5-git-send-email-ehrhardt@linux.vnet.ibm.com> <200808191342.29918.arnd@arndb.de> <48AC13E5.5010503@linux.vnet.ibm.com> <1219257000.14362.90.camel@localhost.localdomain> <1219258333.26429.29.camel@jdub.homelinux.org> <1219259211.14362.94.camel@localhost.localdomain> <20080820151848.69cb8f16@zod.rchland.ibm.com> In-Reply-To: <20080820151848.69cb8f16@zod.rchland.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: linuxppc-dev@ozlabs.org, Arnd Bergmann , kvm-ppc@vger.kernel.org, Hollis Blanchard List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Josh Boyer wrote: > On Wed, 20 Aug 2008 14:06:51 -0500 > Hollis Blanchard wrote: > >>>>> To be honest I unfortunately don't know how big the impact for >>>>> non-virtualized systems is. I would like to test it, but without >>>>> hardware performance counters on the core I have I'm not sure (yet) >>>>> how >>>>> to measure that in a good way - any suggestion welcome. >>>>> >>>> I don't see why we need performance counters. Can't we just compare any >>>> bare metal benchmark results with the patch both applied and not? >>>> >>> Do you know of one that causes a large amount of >>> local_irq_{disable,enable}s to be called? >>> >> I think *every* workload causes a large number of >> local_irq_{disable,enable} calls... :) >> > > Well, sure. I was just going for "test the change as specifically as > possible." One could write a module that did X number of > disable/enable pairs and reported the timebase at start and end to > compare. X could even be a module parameter. Just to try and > eliminate noise or whatever from the testing. > > /me shrugs. > > josh > yeah I thought of something like that too, because I expect the difference to be very small. Instead of a module I wanted to put this somewhere prior to the kernel mounting root-fs to avoid interferences from whatever userspace is doing (e.g. causing thousands of interrupts come back while the module perform that test.). Eventually we need a synthetic benchmark like that AND a check how it affects a common system to be sure. -- Grüsse / regards, Christian Ehrhardt IBM Linux Technology Center, Open Virtualization