Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261542AbVCCGbJ (ORCPT ); Thu, 3 Mar 2005 01:31:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261546AbVCCGXN (ORCPT ); Thu, 3 Mar 2005 01:23:13 -0500 Received: from smtp207.mail.sc5.yahoo.com ([216.136.129.97]:17790 "HELO smtp207.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S261542AbVCCGT4 (ORCPT ); Thu, 3 Mar 2005 01:19:56 -0500 Message-ID: <42274727.2070200@yahoo.com.au> Date: Fri, 04 Mar 2005 04:19:35 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.5) Gecko/20050105 Debian/1.7.5-1 X-Accept-Language: en MIME-Version: 1.0 To: Benjamin Herrenschmidt CC: "David S. Miller" , Paul Mackerras , Andrew Morton , clameter@sgi.com, Linux Kernel list , linux-ia64@vger.kernel.org, Anton Blanchard Subject: Re: Page fault scalability patch V18: Drop first acquisition of ptl References: <20050302174507.7991af94.akpm@osdl.org> <20050302185508.4cd2f618.akpm@osdl.org> <20050302201425.2b994195.akpm@osdl.org> <16934.39386.686708.768378@cargo.ozlabs.ibm.com> <20050302213831.7e6449eb.davem@davemloft.net> <1109829248.5679.178.camel@gaston> In-Reply-To: <1109829248.5679.178.camel@gaston> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1035 Lines: 28 Benjamin Herrenschmidt wrote: >>However, if this pte_cmpxchg() thing is used for removing access, then >>sparc64 can't use it. In such a case a race in the TLB handler would >>result in using an invalid PTE. I could "spin" on some lock bit, but >>there is no way I'm adding instructions to the carefully constructed >>TLB miss handler assembler on sparc64 just for that :-) >> > >Can't you add a lock bit in the PTE itself like we do on ppc64 hash >refill ? > > You don't want to do that for all architectures, as I said earlier. eg. i386 can concurrently set the dirty bit with the MMU (which won't honour the lock). So you then need an atomic lock, atomic pte operations, and atomic unlock where previously you had only the atomic pte operation. This is disastrous for performance. - 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/