Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757460Ab1FIMFf (ORCPT ); Thu, 9 Jun 2011 08:05:35 -0400 Received: from casper.infradead.org ([85.118.1.10]:44959 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757073Ab1FIMFd convert rfc822-to-8bit (ORCPT ); Thu, 9 Jun 2011 08:05:33 -0400 Subject: Re: Change in functionality of futex() system call. From: Peter Zijlstra To: KOSAKI Motohiro Cc: dvhart@linux.intel.com, david@rgmadvisors.com, kyle@moffetthome.net, luto@mit.edu, eric.dumazet@gmail.com, linux-kernel@vger.kernel.org, sbohrer@rgmadvisors.com, zvonler@rgmadvisors.com, hughd@google.com, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <4DF0B072.8060204@jp.fujitsu.com> References: <1307373819.3098.40.camel@edumazet-laptop> <1307376672.2322.167.camel@twins> <1307376989.2322.171.camel@twins> <1307377349.3098.65.camel@edumazet-laptop> <1307377782.2322.183.camel@twins> <1307378564.3098.67.camel@edumazet-laptop> <4DED1421.5000300@linux.intel.com> <1307383898.3098.90.camel@edumazet-laptop> <4DED976C.90009@linux.intel.com> <4DEE3944.5020005@mit.edu> <1307462300.3091.39.camel@edumazet-laptop> <4DEFA18A.2000808@linux.intel.com> <4DF0B072.8060204@jp.fujitsu.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Thu, 09 Jun 2011 14:05:10 +0200 Message-ID: <1307621110.3941.78.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 660 Lines: 15 On Thu, 2011-06-09 at 20:37 +0900, KOSAKI Motohiro wrote: > 1) check the pte of the target address is RW attribute. > 2-1) if yes, it has no COW chance. we can safely use gup result. > 2-2) if no, we have to fallback slow vma walk. maybe, it's okey. > both RO mappings and COW are rare situation. Not so, clean file pages are RO, even if the vma is writable. We use the fault to track dirty state with. -- 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/