Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934736AbaGXWVi (ORCPT ); Thu, 24 Jul 2014 18:21:38 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:43585 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933498AbaGXWVf (ORCPT ); Thu, 24 Jul 2014 18:21:35 -0400 Date: Thu, 24 Jul 2014 15:21:33 -0700 From: Andrew Morton To: Max Filippov Cc: "linux-mm@kvack.org" , Linux-Arch , "Linux/MIPS Mailing List" , "linux-xtensa@linux-xtensa.org" , LKML , Leonid Yegoshin , Chris Zankel , Marc Gauthier Subject: Re: [PATCH v2] mm/highmem: make kmap cache coloring aware Message-Id: <20140724152133.bd4556f632b9cbb506b168cf@linux-foundation.org> In-Reply-To: References: <1405616598-14798-1-git-send-email-jcmvbkbc@gmail.com> <20140723141721.d6a58555f124a7024d010067@linux-foundation.org> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 24 Jul 2014 04:38:01 +0400 Max Filippov wrote: > On Thu, Jul 24, 2014 at 1:17 AM, Andrew Morton > wrote: > > Fifthly, it would be very useful to publish the performance testing > > results for at least one architecture so that we can determine the > > patchset's desirability. And perhaps to motivate other architectures > > to implement this. > > What sort of performance numbers would be relevant? > For xtensa this patch enables highmem use for cores with aliasing cache, > that is access to a gigabyte of memory (typical on KC705 FPGA board) vs. > only 128MBytes of low memory, which is highly desirable. But performance > comparison of these two configurations seems to make little sense. > OTOH performance comparison of highmem variants with and without > cache aliasing would show the quality of our cache flushing code. I'd assumed the patch was making cache coloring available as a performance tweak. But you appear to be saying that the (high) memory is simply unavailable for such cores without this change. I think. Please ensure that v3's changelog explains the full reason for the patch. Assume you're talking to all-the-worlds-an-x86 dummies, OK? -- 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/