From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id 688E88D0039 for ; Thu, 10 Mar 2011 11:38:25 -0500 (EST) Date: Thu, 10 Mar 2011 08:38:09 -0800 From: Andi Kleen 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> Sender: owner-linux-mm@kvack.org List-ID: 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 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, 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org