From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751660AbcDFPds (ORCPT ); Wed, 6 Apr 2016 11:33:48 -0400 Received: from mail-wm0-f54.google.com ([74.125.82.54]:33218 "EHLO mail-wm0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751070AbcDFPdq (ORCPT ); Wed, 6 Apr 2016 11:33:46 -0400 Date: Wed, 6 Apr 2016 17:33:43 +0200 From: Michal Hocko To: Frank Mehnert Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: Re: PG_reserved and compound pages Message-ID: <20160406153343.GJ24272@dhcp22.suse.cz> References: <4482994.u2S3pScRyb@noys2> <20160406150206.GB24283@dhcp22.suse.cz> <3877205.TjDYue2aah@noys2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3877205.TjDYue2aah@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 Wed 06-04-16 17:12:43, Frank Mehnert wrote: > Hi Michal, > > On Wednesday 06 April 2016 17:02:06 Michal Hocko wrote: > > [CCing linux-mm mailing list] > > > > On Wed 06-04-16 13:28:37, Frank Mehnert wrote: > > > Hi, > > > > > > Linux 4.5 introduced additional checks to ensure that compound pages are > > > never marked as reserved. In our code we use PG_reserved to ensure that > > > the kernel does never swap out such pages, e.g. > > > > Are you putting your pages on the LRU list? If not how they could get > > swapped out? > > No, we do nothing like that. It was my understanding that at least with > older kernels it was possible that pages allocated with alloc_pages() > could be swapped out or otherwise manipulated, I might be wrong. I do not see anything like that. All the evictable pages should be on a LRU. > For > instance, it's also necessary that the physical address of the page > is known and that it does never change. I know, there might be problems > with automatic NUMA page migration but that's another story. 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. -- Michal Hocko SUSE Labs