From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756548AbcDGPWj (ORCPT ); Thu, 7 Apr 2016 11:22:39 -0400 Received: from mail-wm0-f42.google.com ([74.125.82.42]:33038 "EHLO mail-wm0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756453AbcDGPWh (ORCPT ); Thu, 7 Apr 2016 11:22:37 -0400 Date: Thu, 7 Apr 2016 17:22:35 +0200 From: Michal Hocko To: Frank Mehnert Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: Re: Re: PG_reserved and compound pages Message-ID: <20160407152234.GE32755@dhcp22.suse.cz> References: <4482994.u2S3pScRyb@noys2> <3877205.TjDYue2aah@noys2> <20160406153343.GJ24272@dhcp22.suse.cz> <20567553.kUaGmfXpqH@noys2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20567553.kUaGmfXpqH@noys2> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 07-04-16 15:45:02, Frank Mehnert wrote: > On Wednesday 06 April 2016 17:33:43 Michal Hocko wrote: [...] > > Do you map your pages to the userspace? If yes then vma with VM_IO or > > VM_PFNMAP should keep any attempt away from those pages. > > Yes, such memory objects are also mapped to userland. Do you think that > VM_IO or VM_PFNMAP would guard against NUMA page migration? Both auto numa and manual numa migration checks vma_migratable and that excludes both VM flags. > Because when > NUMA page migration was introduced (I believe with Linux 3.8) I tested > both flags and saw that they didn't prevent the migration on such VM > areas. Maybe this changed in the meantime, do you have more information > about that? I haven't checked the history much but vma_migratable should be there for quite some time. Maybe it wasn't used in the past. Dunno > The drawback of at least VM_IO is that such memory is not part of a core > dump. that seems to be correct as per vma_dump_size > Actually currently we use vm_insert_page() for userland mapping > and mark the VM areas as > > VM_DONTEXPAND | VM_DONTDUMP but that means that it won't end up in the dump either. Or am I missing your point. -- Michal Hocko SUSE Labs