Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752708Ab1CJQiR (ORCPT ); Thu, 10 Mar 2011 11:38:17 -0500 Received: from mga03.intel.com ([143.182.124.21]:4683 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750819Ab1CJQiP (ORCPT ); Thu, 10 Mar 2011 11:38:15 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.62,296,1297065600"; d="scan'208";a="400694825" Date: Thu, 10 Mar 2011 08:38:09 -0800 From: Andi Kleen To: Stephen Wilson Cc: x86@kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Benjamin Herrenschmidt , Paul Mackerras , Martin Schwidefsky , Heiko Carstens , linux390@de.ibm.com, Paul Mundt , Michel Lespinasse , Andrew Morton , Alexander Viro , linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/5] make *_gate_vma accept mm_struct instead of task_struct II Message-ID: <20110310163809.GA20675@alboin.amr.corp.intel.com> References: <1299630721-4337-1-git-send-email-wilsons@start.ca> <20110310160032.GA20504@alboin.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110310160032.GA20504@alboin.amr.corp.intel.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1481 Lines: 33 On Thu, Mar 10, 2011 at 08:00:32AM -0800, Andi Kleen wrote: > On Tue, Mar 08, 2011 at 07:31:56PM -0500, Stephen Wilson wrote: > > > > Morally, the question of whether an address lies in a gate vma should be asked > > with respect to an mm, not a particular task. > > > > Practically, dropping the dependency on task_struct will help make current and > > future operations on mm's more flexible and convenient. In particular, it > > allows some code paths to avoid the need to hold task_lock. > > > > The only architecture this change impacts in any significant way is x86_64. > > The principle change on that architecture is to mirror TIF_IA32 via > > a new flag in mm_context_t. > > The problem is -- you're adding a likely cache miss on mm_struct for > every 32bit compat syscall now, even if they don't need mm_struct > currently (and a lot of them do not) Unless there's a very good > justification to make up for this performance issue elsewhere > (including numbers) this seems like a bad idea. Hmm I see you're only setting it on exec time actually on rereading the patches. I thought you were changing TS_COMPAT which is in the syscall path. Never mind. I have no problems with doing such a change on exec time. -Andi -- 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/