From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <430A6EB5.2000408@yahoo.com.au> Date: Tue, 23 Aug 2005 10:32:53 +1000 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [RFT][PATCH 0/2] pagefault scalability alternative References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Hugh Dickins , Linus Torvalds , Andrew Morton , linux-mm@kvack.org List-ID: 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. We actually did see that load in handle_pte_fault being cut in half by a store. I wouldn't be too worried about that though, as it's only for PAE. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com -- 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