From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 01 Aug 2002 17:43:01 -0700 (PDT) Message-Id: <20020801.174301.123634127.davem@redhat.com> Subject: Re: large page patch From: "David S. Miller" In-Reply-To: <3D49D45A.D68CCFB4@zip.com.au> References: <3D49D45A.D68CCFB4@zip.com.au> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: akpm@zip.com.au Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, rohit.seth@intel.com, sunil.saxena@intel.com, asit.k.mallick@intel.com List-ID: Some observations which have been made thus far: - Minimal impact on the VM and MM layers Well the downside of this is that it means it isn't transparent to userspace. For example, specfp2000 results aren't going to improve after installing these changes. Some of the other large page implementations would. - The change to MAX_ORDER is unneeded This is probably done to increase the likelyhood that 4MB page orders are available. If we collapse 4MB pages deeper, they are less likely to be broken up because smaller orders would be selected first. Maybe it doesn't make a difference.... - swapping of large pages and making them pagecache-coherent is unpopular. Swapping them is easy, any time you hit a large PTE you unlarge it. This is what some of other large page implementations do. Basically the implementation is that set_pte() breaks apart large ptes when necessary. I agree on the pagecache side. Actually to be honest the other implementations seemed less intrusive and easier to add support for. The downside is that handling of weird cases like x86 using pmd's for 4MB pages was not complete last time I checked. -- 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/