From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f53.google.com (mail-oi0-f53.google.com [209.85.218.53]) by kanga.kvack.org (Postfix) with ESMTP id 02A8E6B0255 for ; Sun, 28 Feb 2016 19:03:42 -0500 (EST) Received: by mail-oi0-f53.google.com with SMTP id d205so12087512oia.0 for ; Sun, 28 Feb 2016 16:03:41 -0800 (PST) Received: from mail-oi0-x231.google.com (mail-oi0-x231.google.com. [2607:f8b0:4003:c06::231]) by mx.google.com with ESMTPS id a4si19388130obh.8.2016.02.28.16.03.41 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 28 Feb 2016 16:03:41 -0800 (PST) Received: by mail-oi0-x231.google.com with SMTP id k67so37664556oia.3 for ; Sun, 28 Feb 2016 16:03:41 -0800 (PST) Date: Sun, 28 Feb 2016 16:03:38 -0800 (PST) From: Hugh Dickins Subject: Re: [RFC PATCH] proc: do not include shmem and driver pages in /proc/meminfo::Cached In-Reply-To: <20160219131307.a38646706cc514fcaf18793a@linux-foundation.org> Message-ID: References: <1455827801-13082-1-git-send-email-hannes@cmpxchg.org> <20160219131307.a38646706cc514fcaf18793a@linux-foundation.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Konstantin Khlebnikov , Hugh Dickins , Johannes Weiner , "linux-mm@kvack.org" , Rik van Riel , Mel Gorman , Linux Kernel Mailing List , kernel-team@fb.com On Fri, 19 Feb 2016, Andrew Morton wrote: > On Fri, 19 Feb 2016 09:40:45 +0300 Konstantin Khlebnikov wrote: > > > >> What are your thoughts on this? > > > > > > My thoughts are NAK. A misleading stat is not so bad as a > > > misleading stat whose meaning we change in some random kernel. > > > > > > By all means improve Documentation/filesystems/proc.txt on Cached. > > > By all means promote Active(file)+Inactive(file)-Buffers as often a > > > better measure (though Buffers itself is obscure to me - is it intended > > > usually to approximate resident FS metadata?). By all means work on > > > /proc/meminfo-v2 (though that may entail dispiritingly long discussions). > > > > > > We have to assume that Cached has been useful to some people, and that > > > they've learnt to subtract Shmem from it, if slow or no swap concerns them. > > > > > > Added Konstantin to Cc: he's had valuable experience of people learning > > > to adapt to the numbers that we put out. > > > > > > > I think everything will ok. Subtraction of shmem isn't widespread practice, > > more like secret knowledge. This wasn't documented and people who use > > this should be aware that this might stop working at any time. So, ACK. > > It worries me as well - we're deliberately altering the behaviour of > existing userspace code. Not all of those alterations will be welcome! > > We could add a shiny new field into meminfo and train people to migrate > to that. But that would just be a sum of already-available fields. In > an ideal world we could solve all of this with documentation and > cluebatting (and some apologizing!). Ah, I missed this, and just sent a redundant addition to the thread; followed by this doubly redundant addition. Hugh -- 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