From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id C9BBC6B0253 for ; Fri, 15 Sep 2017 10:16:25 -0400 (EDT) Received: by mail-pg0-f69.google.com with SMTP id 6so4971728pgh.0 for ; Fri, 15 Sep 2017 07:16:25 -0700 (PDT) Received: from mga02.intel.com (mga02.intel.com. [134.134.136.20]) by mx.google.com with ESMTPS id h14si765102plk.375.2017.09.15.07.16.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 Sep 2017 07:16:24 -0700 (PDT) Subject: Re: [PATCH 1/3] mm, sysctl: make VM stats configurable 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> From: Dave Hansen Message-ID: Date: Fri, 15 Sep 2017 07:16:23 -0700 MIME-Version: 1.0 In-Reply-To: <20170915114952.czb7nbsioqguxxk3@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko , Kemi Wang Cc: "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 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. > 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. 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. A single-time printk could also go a long way to keeping folks from getting confused. -- 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