Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753481AbaJGKrV (ORCPT ); Tue, 7 Oct 2014 06:47:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:22739 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752825AbaJGKrS (ORCPT ); Tue, 7 Oct 2014 06:47:18 -0400 Date: Tue, 7 Oct 2014 11:46:04 +0100 From: "Dr. David Alan Gilbert" To: "Kirill A. Shutemov" Cc: Andrea Arcangeli , qemu-devel@nongnu.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, Linus Torvalds , Andres Lagar-Cavilla , Dave Hansen , Paolo Bonzini , Rik van Riel , Mel Gorman , Andy Lutomirski , Andrew Morton , Sasha Levin , Hugh Dickins , Peter Feiner , "\\\"Dr. David Alan Gilbert\\\"" , Christopher Covington , Johannes Weiner , Android Kernel Team , Robert Love , Dmitry Adamushko , Neil Brown , Mike Hommey , Taras Glek , Jan Kara , KOSAKI Motohiro , Michel Lespinasse , Minchan Kim , Keith Packard , "Huangpeng (Peter)" , Isaku Yamahata , Anthony Liguori , Stefan Hajnoczi , Wenchao Xia , Andrew Jones , Juan Quintela Subject: Re: [PATCH 08/17] mm: madvise MADV_USERFAULT Message-ID: <20141007104603.GI2404@work-vm> References: <1412356087-16115-1-git-send-email-aarcange@redhat.com> <1412356087-16115-9-git-send-email-aarcange@redhat.com> <20141007103645.GB30762@node.dhcp.inet.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141007103645.GB30762@node.dhcp.inet.fi> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Kirill A. Shutemov (kirill@shutemov.name) wrote: > On Fri, Oct 03, 2014 at 07:07:58PM +0200, Andrea Arcangeli wrote: > > MADV_USERFAULT is a new madvise flag that will set VM_USERFAULT in the > > vma flags. Whenever VM_USERFAULT is set in an anonymous vma, if > > userland touches a still unmapped virtual address, a sigbus signal is > > sent instead of allocating a new page. The sigbus signal handler will > > then resolve the page fault in userland by calling the > > remap_anon_pages syscall. > > Hm. I wounder if this functionality really fits madvise(2) interface: as > far as I understand it, it provides a way to give a *hint* to kernel which > may or may not trigger an action from kernel side. I don't think an > application will behaive reasonably if kernel ignore the *advise* and will > not send SIGBUS, but allocate memory. Aren't DONTNEED and DONTDUMP similar cases of madvise operations that are expected to do what they say ? > I would suggest to consider to use some other interface for the > functionality: a new syscall or, perhaps, mprotect(). Dave > -- > Kirill A. Shutemov -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK -- 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/