From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qc0-f176.google.com (mail-qc0-f176.google.com [209.85.216.176]) by kanga.kvack.org (Postfix) with ESMTP id 6E9056B0031 for ; Fri, 27 Dec 2013 14:47:52 -0500 (EST) Received: by mail-qc0-f176.google.com with SMTP id i8so8940756qcq.7 for ; Fri, 27 Dec 2013 11:47:52 -0800 (PST) Received: from blu0-omc4-s5.blu0.hotmail.com (blu0-omc4-s5.blu0.hotmail.com. [65.55.111.144]) by mx.google.com with ESMTP id l2si1610191qaf.38.2013.12.27.11.47.51 for ; Fri, 27 Dec 2013 11:47:51 -0800 (PST) Message-ID: From: John David Anglin In-Reply-To: <20131227193330.GE4945@linux.intel.com> Subject: Re: [PATCH] remap_file_pages needs to check for cache coherency References: <20131227180018.GC4945@linux.intel.com> <20131227193330.GE4945@linux.intel.com> Content-Type: text/plain; charset="US-ASCII"; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit MIME-Version: 1.0 (Apple Message framework v936) Date: Fri, 27 Dec 2013 14:47:32 -0500 Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: linux-mm@kvack.org, "David S. Miller" , sparclinux@vger.kernel.org, linux-parisc@vger.kernel.org, linux-mips@linux-mips.org On 27-Dec-13, at 2:33 PM, Matthew Wilcox wrote: > Have you considered measuring SHMLBA on different CPU models and > reducing it at boot time? I know that 4MB is the architectural > guarantee > (actually, I seem to remember that 16MB was the architectural > guarantee, > but jsm found some CPU architects who said it would enver exceed 4MB). > I bet some CPUs have considerably lower cache coherency limits. It's worth looking at. The value is supposed to be returned by the PDC_CACHE PDC call but I know my rp3440 returns a value of 0 indicating that the aliasing boundary is unknown and may be greater than 16MB. Dave -- John David Anglin dave.anglin@bell.net -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org