From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx180.postini.com [74.125.245.180]) by kanga.kvack.org (Postfix) with SMTP id 48F866B0099 for ; Wed, 17 Apr 2013 10:18:49 -0400 (EDT) Message-ID: <516EAF31.8000107@linux.intel.com> Date: Wed, 17 Apr 2013 07:18:25 -0700 From: Darren Hart MIME-Version: 1.0 Subject: Re: [PATCH] futex: bugfix for futex-key conflict when futex use hugepage References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: zhang.yi20@zte.com.cn Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Dave Hansen On 04/17/2013 02:55 AM, zhang.yi20@zte.com.cn wrote: > Darren Hart wrote on 2013/04/17 01:57:10: > >> Again, a functional testcase in futextest would be a good idea. This >> helps validate the patch and also can be used to identify regressions in >> the future. > > I will post the testcase code later. > >> >> What is the max value of comp_idx? Are we at risk of truncating it? >> Looks like not really from my initial look. >> >> This also needs a comment in futex.h describing the usage of the offset >> field in union futex_key as well as above get_futex_key describing the >> key for shared mappings. >> >> > > As far as I know , the max size of one hugepage is 1 GBytes for x86 cpu. > Can some other cpus support greater hugepage even more than 4 GBytes? If > so, we can change the type of 'offset' from int to long to avoid > truncating. I discussed this with Dave Hansen, on CC, and he thought we needed 9 bits, so even on x86 32b we should be covered. -- Darren Hart Intel Open Source Technology Center Yocto Project - Technical Lead - Linux Kernel -- 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