From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id B0A1B6B0253 for ; Fri, 15 Sep 2017 10:28:28 -0400 (EDT) Received: by mail-wr0-f199.google.com with SMTP id h16so2627973wrf.0 for ; Fri, 15 Sep 2017 07:28:28 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id q20si1337852edc.108.2017.09.15.07.28.27 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 15 Sep 2017 07:28:27 -0700 (PDT) Date: Fri, 15 Sep 2017 16:28:23 +0200 From: Michal Hocko Subject: Re: [PATCH 1/3] mm, sysctl: make VM stats configurable Message-ID: <20170915142823.jlhsba6rdhx5glfe@dhcp22.suse.cz> References: <1505467406-9945-1-git-send-email-kemi.wang@intel.com> <1505467406-9945-2-git-send-email-kemi.wang@intel.com> <20170915114952.czb7nbsioqguxxk3@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: Kemi Wang , "Luis R . Rodriguez" , Kees Cook , Andrew Morton , Jonathan Corbet , Mel Gorman , Johannes Weiner , Christopher Lameter , Sebastian Andrzej Siewior , Vlastimil Babka , Hillf Danton , Tim Chen , Andi Kleen , Jesper Dangaard Brouer , Ying Huang , Aaron Lu , Proc sysctl , Linux MM , Linux Kernel On Fri 15-09-17 07:16:23, Dave Hansen wrote: > On 09/15/2017 04:49 AM, Michal Hocko wrote: > > Why do we need an auto-mode? Is it safe to enforce by default. > > Do we *need* it? Not really. > > But, it does offer the best of both worlds: The vast majority of users > see virtually no impact from the counters. The minority that do need > them pay the cost *and* don't have to change their tooling at all. Just to make it clear, I am not really opposing. It just adds some code which we can safe... It is also rather chatty for something that can be true/false. > > Is it> possible that userspace can get confused to see 0 NUMA stats in > the > > first read while other allocation stats are non-zero? > > I doubt it. Those counters are pretty worthless by themselves. I have > tooling that goes and reads them, but it aways displays deltas. Read > stats, sleep one second, read again, print the difference. This is how I use them as well. > The only scenario I can see mattering is someone who is seeing a > performance issue due to NUMA allocation misses (or whatever) and wants > to go look *back* in the past. yes > A single-time printk could also go a long way to keeping folks from > getting confused. -- Michal Hocko SUSE Labs -- 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