From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 23 Aug 2005 08:04:49 +0100 (BST) From: Hugh Dickins Subject: Re: [RFT][PATCH 0/2] pagefault scalability alternative In-Reply-To: <430A6EB5.2000408@yahoo.com.au> Message-ID: References: <430A6EB5.2000408@yahoo.com.au> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Christoph Lameter , Linus Torvalds , Andrew Morton , linux-mm@kvack.org List-ID: On Tue, 23 Aug 2005, Nick Piggin wrote: > Christoph Lameter wrote: > > > The patch generally drops the first acquisition of the page table lock > > from handle_mm_fault that is used to protect the read operations on the > > page table. I doubt that this works with i386 PAE since the page table > > read operations are not protected by the ptl. These are 64 bit which > > cannot be reliably retrieved in an 32 bit operation on i386 as you > > pointed out last fall. There may be concurrent writes so that one gets > > two pieces that do not fit. PAE mode either needs to fall back to take > > the page_table_lock for reads or use some tricks to guarantee 64bit > > atomicity. > > Oh yes, you need 64-bit atomic reads and writes for that. I don't believe we do. Let me expand on that in my reply to Christoph. Hugh -- 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