From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966126AbbD2D6N (ORCPT ); Tue, 28 Apr 2015 23:58:13 -0400 Received: from mail-pd0-f171.google.com ([209.85.192.171]:34113 "EHLO mail-pd0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965853AbbD2D6K (ORCPT ); Tue, 28 Apr 2015 23:58:10 -0400 Date: Wed, 29 Apr 2015 12:57:22 +0900 From: Minchan Kim To: Vladimir Davydov Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Greg Thelen , Michel Lespinasse , David Rientjes , Pavel Emelyanov , Cyrill Gorcunov , Jonathan Corbet , linux-api@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/3] idle memory tracking Message-ID: <20150429035722.GA11486@blaptop> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Vladimir, On Tue, Apr 28, 2015 at 03:24:39PM +0300, Vladimir Davydov wrote: > Hi, > > This patch set introduces a new user API for tracking user memory pages > that have not been used for a given period of time. The purpose of this > is to provide the userspace with the means of tracking a workload's > working set, i.e. the set of pages that are actively used by the > workload. Knowing the working set size can be useful for partitioning > the system more efficiently, e.g. by tuning memory cgroup limits > appropriately, or for job placement within a compute cluster. > > ---- USE CASES ---- > > The unified cgroup hierarchy has memory.low and memory.high knobs, which > are defined as the low and high boundaries for the workload working set > size. However, the working set size of a workload may be unknown or > change in time. With this patch set, one can periodically estimate the > amount of memory unused by each cgroup and tune their memory.low and > memory.high parameters accordingly, therefore optimizing the overall > memory utilization. > > Another use case is balancing workloads within a compute cluster. > Knowing how much memory is not really used by a workload unit may help > take a more optimal decision when considering migrating the unit to > another node within the cluster. > > ---- USER API ---- > > The user API consists of two new proc files: > > * /proc/kpageidle. For each page this file contains a 64-bit number, which > equals 1 if the page is idle or 0 otherwise, indexed by PFN. A page is Why do we need 64bit per page to indicate just idle or not? What do you imagine we're happy with other 63bit in future? -- Kind regards, Minchan Kim