From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [PATCH 0/3] Virtual huge zero page Date: Mon, 01 Oct 2012 10:33:12 -0700 Message-ID: <5069D3D8.9070805@linux.intel.com> References: <1348875441-19561-1-git-send-email-kirill.shutemov@linux.intel.com> <20120929134811.GC26989@redhat.com> <5069B804.6040902@linux.intel.com> <20121001163118.GC18051@redhat.com> <5069CCF9.7040309@linux.intel.com> <20121001172624.GD18051@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20121001172624.GD18051@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Andrea Arcangeli Cc: "Kirill A. Shutemov" , Andrew Morton , linux-mm@kvack.org, Andi Kleen , linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , Arnd Bergmann , Ingo Molnar , linux-arch@vger.kernel.org List-Id: linux-arch.vger.kernel.org On 10/01/2012 10:26 AM, Andrea Arcangeli wrote: > >> It is well known that microbenchmarks can be horribly misleading. What >> led to Kirill investigating huge zero page in the first place was the >> fact that some applications/macrobenchmarks benefit, and I think those >> are the right thing to look at. > > The whole point of the two microbenchmarks was to measure the worst > cases for both scenarios and I think that was useful. Real life using > zero pages are going to be somewhere in that range. > ... and I think it would be worthwhile to know which effect dominates (or neither, in which case it doesn't matter). Overall, I'm okay with either as long as we don't lock down 2 MB when there isn't a huge zero page in use. -hpa From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com ([192.55.52.93]:17754 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750856Ab2JARdN (ORCPT ); Mon, 1 Oct 2012 13:33:13 -0400 Message-ID: <5069D3D8.9070805@linux.intel.com> Date: Mon, 01 Oct 2012 10:33:12 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: [PATCH 0/3] Virtual huge zero page References: <1348875441-19561-1-git-send-email-kirill.shutemov@linux.intel.com> <20120929134811.GC26989@redhat.com> <5069B804.6040902@linux.intel.com> <20121001163118.GC18051@redhat.com> <5069CCF9.7040309@linux.intel.com> <20121001172624.GD18051@redhat.com> In-Reply-To: <20121001172624.GD18051@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Andrea Arcangeli Cc: "Kirill A. Shutemov" , Andrew Morton , linux-mm@kvack.org, Andi Kleen , linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , Arnd Bergmann , Ingo Molnar , linux-arch@vger.kernel.org Message-ID: <20121001173312.1tX8uEbdrg64tUfGJL1KsiBUTaYH_kYjvXw5tTMUmd0@z> On 10/01/2012 10:26 AM, Andrea Arcangeli wrote: > >> It is well known that microbenchmarks can be horribly misleading. What >> led to Kirill investigating huge zero page in the first place was the >> fact that some applications/macrobenchmarks benefit, and I think those >> are the right thing to look at. > > The whole point of the two microbenchmarks was to measure the worst > cases for both scenarios and I think that was useful. Real life using > zero pages are going to be somewhere in that range. > ... and I think it would be worthwhile to know which effect dominates (or neither, in which case it doesn't matter). Overall, I'm okay with either as long as we don't lock down 2 MB when there isn't a huge zero page in use. -hpa