From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 551426B0253 for ; Fri, 21 Oct 2016 07:17:37 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id n85so50265308pfi.7 for ; Fri, 21 Oct 2016 04:17:37 -0700 (PDT) Received: from ipmail04.adl6.internode.on.net (ipmail04.adl6.internode.on.net. [150.101.137.141]) by mx.google.com with ESMTP id t25si2292555pge.118.2016.10.21.04.17.35 for ; Fri, 21 Oct 2016 04:17:36 -0700 (PDT) Date: Fri, 21 Oct 2016 22:17:32 +1100 From: Dave Chinner Subject: Re: [RFC] fs/proc/meminfo: introduce Unaccounted statistic Message-ID: <20161021111732.GR14023@dastard> References: <20161020121149.9935-1-vbabka@suse.cz> <20161020133358.GN14609@dhcp22.suse.cz> <20161020225929.GP23194@dastard> <70fe5da3-c739-58ce-0531-299b48e0ca9e@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <70fe5da3-c739-58ce-0531-299b48e0ca9e@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Mel Gorman , Johannes Weiner , "Kirill A. Shutemov" , Hugh Dickins , David Rientjes On Fri, Oct 21, 2016 at 09:25:10AM +0200, Vlastimil Babka wrote: > On 10/21/2016 12:59 AM, Dave Chinner wrote: > >On Thu, Oct 20, 2016 at 03:33:58PM +0200, Michal Hocko wrote: > >>On Thu 20-10-16 14:11:49, Vlastimil Babka wrote: > >>[...] > >>> Hi, I'm wondering if people would find this useful. If you think it is, and > >>> to not make performance worse, I could also make sure in proper submission > >>> that values are not read via global_page_state() multiple times etc... > >> > >>I definitely find this information useful and hate to do the math all > >>the time but on the other hand this is quite fragile and I can imagine > >>we can easily forget to add something there and provide a misleading > >>information to the userspace. So I would be worried with a long term > >>maintainability of this. > > > >This will result in valid memory usage by subsystems like the XFS > >buffer cache being reported as "unaccounted". Given this cache > >(whose size is shrinker controlled) can grow to gigabytes in size > >under various metadata intensive workloads, there's every chance > >that such reporting will make users incorrectly think they have a > >massive memory leak.... > > Is the XFS buffer cache accounted (and visible) somewhere then? I'd > say getting such large consumers to become visible on the same level > as others would be another advantage... It's handles are visible via the xfs_buf slab cache. By the time you've got enough memory in the buffer cache for it to be noticed, the xfs_buf slab is near the top of the list in slabtop. Of course, because of the crazy way slub names caches, this can be impossible to find because there isn't a "xfs_buf" slab cache that shows up in slabtop. It'll end being called something like "mnt_cache".... Cheers, Dave. -- Dave Chinner david@fromorbit.com -- 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