From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Kirill A. Shutemov" Subject: Re: [Qemu-devel] [PATCH 10/17] mm: rmap preparation for remap_anon_pages Date: Tue, 7 Oct 2014 14:10:26 +0300 Message-ID: <20141007111026.GD30762@node.dhcp.inet.fi> References: <1412356087-16115-1-git-send-email-aarcange@redhat.com> <1412356087-16115-11-git-send-email-aarcange@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1412356087-16115-11-git-send-email-aarcange@redhat.com> Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, Robert Love , Dave Hansen , Jan Kara , Neil Brown , Stefan Hajnoczi , Andrew Jones , KOSAKI Motohiro , Michel Lespinasse , Taras Glek , Juan Quintela , Hugh Dickins , Isaku Yamahata , Mel Gorman , Sasha Levin , Android Kernel Team , "\\\"Dr. David Alan Gilbert\\\"" , "Huangpeng (Peter)" , Andres Lagar-Cavilla , Christopher Covington , Anthony Liguori List-Id: linux-api@vger.kernel.org On Fri, Oct 03, 2014 at 07:08:00PM +0200, Andrea Arcangeli wrote: > There's one constraint enforced to allow this simplification: the > source pages passed to remap_anon_pages must be mapped only in one > vma, but this is not a limitation when used to handle userland page > faults with MADV_USERFAULT. The source addresses passed to > remap_anon_pages should be set as VM_DONTCOPY with MADV_DONTFORK to > avoid any risk of the mapcount of the pages increasing, if fork runs > in parallel in another thread, before or while remap_anon_pages runs. Have you considered triggering COW instead of adding limitation on pages' mapcount? The limitation looks artificial from interface POV. -- Kirill A. Shutemov -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Kirill A. Shutemov" Subject: Re: [Qemu-devel] [PATCH 10/17] mm: rmap preparation for remap_anon_pages Date: Tue, 7 Oct 2014 14:10:26 +0300 Message-ID: <20141007111026.GD30762@node.dhcp.inet.fi> References: <1412356087-16115-1-git-send-email-aarcange@redhat.com> <1412356087-16115-11-git-send-email-aarcange@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, Robert Love , Dave Hansen , Jan Kara , Neil Brown , Stefan Hajnoczi , Andrew Jones , KOSAKI Motohiro , Michel Lespinasse , Taras Glek , Juan Quintela , Hugh Dickins , Isaku Yamahata , Mel Gorman , Sasha Levin , Android Kernel Team , "\\\"Dr. David Alan Gilbert\\\"" , "Huangpeng (Peter)" , Andres Lagar-Cavilla , Christopher Covington , Anthony Liguori Return-path: Content-Disposition: inline In-Reply-To: <1412356087-16115-11-git-send-email-aarcange@redhat.com> Sender: owner-linux-mm@kvack.org List-Id: kvm.vger.kernel.org On Fri, Oct 03, 2014 at 07:08:00PM +0200, Andrea Arcangeli wrote: > There's one constraint enforced to allow this simplification: the > source pages passed to remap_anon_pages must be mapped only in one > vma, but this is not a limitation when used to handle userland page > faults with MADV_USERFAULT. The source addresses passed to > remap_anon_pages should be set as VM_DONTCOPY with MADV_DONTFORK to > avoid any risk of the mapcount of the pages increasing, if fork runs > in parallel in another thread, before or while remap_anon_pages runs. Have you considered triggering COW instead of adding limitation on pages' mapcount? The limitation looks artificial from interface POV. -- Kirill A. Shutemov -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f172.google.com (mail-wi0-f172.google.com [209.85.212.172]) by kanga.kvack.org (Postfix) with ESMTP id 883CD6B0038 for ; Tue, 7 Oct 2014 07:10:53 -0400 (EDT) Received: by mail-wi0-f172.google.com with SMTP id n3so7425140wiv.17 for ; Tue, 07 Oct 2014 04:10:52 -0700 (PDT) Received: from kirsi1.inet.fi (mta-out1.inet.fi. [62.71.2.234]) by mx.google.com with ESMTP id ba7si20464884wjc.158.2014.10.07.04.10.52 for ; Tue, 07 Oct 2014 04:10:52 -0700 (PDT) Date: Tue, 7 Oct 2014 14:10:26 +0300 From: "Kirill A. Shutemov" Subject: Re: [Qemu-devel] [PATCH 10/17] mm: rmap preparation for remap_anon_pages Message-ID: <20141007111026.GD30762@node.dhcp.inet.fi> References: <1412356087-16115-1-git-send-email-aarcange@redhat.com> <1412356087-16115-11-git-send-email-aarcange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1412356087-16115-11-git-send-email-aarcange@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, Robert Love , Dave Hansen , Jan Kara , Neil Brown , Stefan Hajnoczi , Andrew Jones , KOSAKI Motohiro , Michel Lespinasse , Taras Glek , Juan Quintela , Hugh Dickins , Isaku Yamahata , Mel Gorman , Sasha Levin , Android Kernel Team , "\\\"Dr. David Alan Gilbert\\\"" , "Huangpeng (Peter)" , Andres Lagar-Cavilla , Christopher Covington , Anthony Liguori , Paolo Bonzini , Keith Packard , Wenchao Xia , Andy Lutomirski , Minchan Kim , Dmitry Adamushko , Johannes Weiner , Mike Hommey , Andrew Morton , Linus Torvalds , Peter Feiner On Fri, Oct 03, 2014 at 07:08:00PM +0200, Andrea Arcangeli wrote: > There's one constraint enforced to allow this simplification: the > source pages passed to remap_anon_pages must be mapped only in one > vma, but this is not a limitation when used to handle userland page > faults with MADV_USERFAULT. The source addresses passed to > remap_anon_pages should be set as VM_DONTCOPY with MADV_DONTFORK to > avoid any risk of the mapcount of the pages increasing, if fork runs > in parallel in another thread, before or while remap_anon_pages runs. Have you considered triggering COW instead of adding limitation on pages' mapcount? The limitation looks artificial from interface POV. -- Kirill A. Shutemov -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753729AbaJGLLR (ORCPT ); Tue, 7 Oct 2014 07:11:17 -0400 Received: from mta-out1.inet.fi ([62.71.2.197]:35298 "EHLO kirsi1.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753236AbaJGLLN (ORCPT ); Tue, 7 Oct 2014 07:11:13 -0400 Date: Tue, 7 Oct 2014 14:10:26 +0300 From: "Kirill A. Shutemov" To: Andrea Arcangeli Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, Robert Love , Dave Hansen , Jan Kara , Neil Brown , Stefan Hajnoczi , Andrew Jones , KOSAKI Motohiro , Michel Lespinasse , Taras Glek , Juan Quintela , Hugh Dickins , Isaku Yamahata , Mel Gorman , Sasha Levin , Android Kernel Team , "\\\"Dr. David Alan Gilbert\\\"" , "Huangpeng (Peter)" , Andres Lagar-Cavilla , Christopher Covington , Anthony Liguori , Paolo Bonzini , Keith Packard , Wenchao Xia , Andy Lutomirski , Minchan Kim , Dmitry Adamushko , Johannes Weiner , Mike Hommey , Andrew Morton , Linus Torvalds , Peter Feiner Subject: Re: [Qemu-devel] [PATCH 10/17] mm: rmap preparation for remap_anon_pages Message-ID: <20141007111026.GD30762@node.dhcp.inet.fi> References: <1412356087-16115-1-git-send-email-aarcange@redhat.com> <1412356087-16115-11-git-send-email-aarcange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1412356087-16115-11-git-send-email-aarcange@redhat.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 03, 2014 at 07:08:00PM +0200, Andrea Arcangeli wrote: > There's one constraint enforced to allow this simplification: the > source pages passed to remap_anon_pages must be mapped only in one > vma, but this is not a limitation when used to handle userland page > faults with MADV_USERFAULT. The source addresses passed to > remap_anon_pages should be set as VM_DONTCOPY with MADV_DONTFORK to > avoid any risk of the mapcount of the pages increasing, if fork runs > in parallel in another thread, before or while remap_anon_pages runs. Have you considered triggering COW instead of adding limitation on pages' mapcount? The limitation looks artificial from interface POV. -- Kirill A. Shutemov From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54109) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XbSfV-0001HJ-Bl for qemu-devel@nongnu.org; Tue, 07 Oct 2014 07:11:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XbSfP-0003ii-G8 for qemu-devel@nongnu.org; Tue, 07 Oct 2014 07:11:01 -0400 Received: from mta-out1.inet.fi ([62.71.2.226]:46101 helo=kirsi1.inet.fi) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XbSfP-0003iT-6b for qemu-devel@nongnu.org; Tue, 07 Oct 2014 07:10:55 -0400 Date: Tue, 7 Oct 2014 14:10:26 +0300 From: "Kirill A. Shutemov" Message-ID: <20141007111026.GD30762@node.dhcp.inet.fi> References: <1412356087-16115-1-git-send-email-aarcange@redhat.com> <1412356087-16115-11-git-send-email-aarcange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1412356087-16115-11-git-send-email-aarcange@redhat.com> Subject: Re: [Qemu-devel] [PATCH 10/17] mm: rmap preparation for remap_anon_pages List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Andrea Arcangeli Cc: Robert Love , Dave Hansen , Jan Kara , kvm@vger.kernel.org, Neil Brown , Stefan Hajnoczi , qemu-devel@nongnu.org, linux-mm@kvack.org, KOSAKI Motohiro , Michel Lespinasse , Taras Glek , Juan Quintela , Hugh Dickins , Isaku Yamahata , Mel Gorman , Sasha Levin , Android Kernel Team , Andrew Jones , "Huangpeng (Peter)" , "\\\"Dr. David Alan Gilbert\\\"" , Andres Lagar-Cavilla , Christopher Covington , Anthony Liguori , Mike Hommey , Keith Packard , Wenchao Xia , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Andy Lutomirski , Minchan Kim , Dmitry Adamushko , Johannes Weiner , Paolo Bonzini , Andrew Morton , Linus Torvalds , Peter Feiner On Fri, Oct 03, 2014 at 07:08:00PM +0200, Andrea Arcangeli wrote: > There's one constraint enforced to allow this simplification: the > source pages passed to remap_anon_pages must be mapped only in one > vma, but this is not a limitation when used to handle userland page > faults with MADV_USERFAULT. The source addresses passed to > remap_anon_pages should be set as VM_DONTCOPY with MADV_DONTFORK to > avoid any risk of the mapcount of the pages increasing, if fork runs > in parallel in another thread, before or while remap_anon_pages runs. Have you considered triggering COW instead of adding limitation on pages' mapcount? The limitation looks artificial from interface POV. -- Kirill A. Shutemov