From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754222AbaIORcq (ORCPT ); Mon, 15 Sep 2014 13:32:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59749 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753957AbaIORco (ORCPT ); Mon, 15 Sep 2014 13:32:44 -0400 Date: Mon, 15 Sep 2014 19:29:24 +0200 From: Oleg Nesterov To: Jerome Marchand Cc: linux-mm@kvack.org, Randy Dunlap , Martin Schwidefsky , Heiko Carstens , linux390@de.ibm.com, Hugh Dickins , Peter Zijlstra , Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Subject: Re: [RFC PATCH v2 5/5] mm, shmem: Show location of non-resident shmem pages in smaps Message-ID: <20140915172923.GA26275@redhat.com> References: <1410791077-5300-1-git-send-email-jmarchan@redhat.com> <1410791077-5300-6-git-send-email-jmarchan@redhat.com> <20140915162131.GA22768@redhat.com> <54171829.3090108@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54171829.3090108@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/15, Jerome Marchand wrote: > > On 09/15/2014 06:21 PM, Oleg Nesterov wrote: > > Hi Jerome, > > > > Not sure I understand this patch correctly, will try to read it later. > > But a couple of nits/questions anyway, > > > > On 09/15, Jerome Marchand wrote: > >> > >> +The ShmXXX lines only appears for shmem mapping. They show the amount of memory > >> +from the mapping that is currently: > >> + - resident in RAM but not mapped into any process (ShmNotMapped) > > > > But how can we know that it is not mapped by another process? > > Its mapcount is zero. Ah, yes, I missed the "!count" check. Thanks! > > And in fact "not mapped" looks confusing (at least to me). > > "Not mapped" as "not present in a page table". It does belong to a > userspace mapping though. I wonder if there is a less ambiguous terminology. To me "not present in page tables" looks more understandable, but I won't insist. > > IIUC it is actually > > mapped even by this process, just it never tried to fault these (resident or > > swapped) pages in. Right? > > No these pages are in the page cache. This can happen when the only > process which have accessed these exits or munmap() the mapping. Yes, yes, I meant that this process didn't touch these pages and thus pte_none() == T. > > And I am not sure why we ignore SHMEM_SWAPCACHE... > > Hugh didn't like it as it is a small and transient value. OK, but perhaps update_shmem_stats() should treat it as SHMEM_SWAP. Nevermind, I leave this to you and Hugh. Oleg.