From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754844AbYIXTXe (ORCPT ); Wed, 24 Sep 2008 15:23:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752065AbYIXTXZ (ORCPT ); Wed, 24 Sep 2008 15:23:25 -0400 Received: from e1.ny.us.ibm.com ([32.97.182.141]:56722 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752337AbYIXTXY (ORCPT ); Wed, 24 Sep 2008 15:23:24 -0400 Subject: Re: [PATCH 1/2] Report the pagesize backing a VMA in /proc/pid/smaps From: Dave Hansen To: Mel Gorman Cc: KOSAKI Motohiro , agl@us.ibm.com, LKML , Linux-MM In-Reply-To: <20080924191107.GA31324@csn.ul.ie> References: <20080923211140.DC16.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20080923194655.GA25542@csn.ul.ie> <20080924210309.8C3B.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20080924154120.GA10837@csn.ul.ie> <1222272395.15523.3.camel@nimitz> <20080924171003.GD10837@csn.ul.ie> <1222282749.15523.59.camel@nimitz> <20080924191107.GA31324@csn.ul.ie> Content-Type: text/plain Date: Wed, 24 Sep 2008 12:23:10 -0700 Message-Id: <1222284190.15523.64.camel@nimitz> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2008-09-24 at 20:11 +0100, Mel Gorman wrote: > I don't get what you mean by it being sprinkled in each smaps file. How > would you present the data? 1. figure out what the file path is from smaps 2. look up the mount 3. look up the page sizes from the mount's information > > We should be able to figure out which > > mount the file is from and, from there, maybe we need some per-mount > > information exported. > > Per-mount information is already exported and you can infer the data about > huge pagesizes. For example, if you know the default huge pagesize (from > /proc/meminfo), and the file is on hugetlbfs (read maps, then /proc/mounts) > and there is no pagesize= mount option (mounts again), you could guess what the > hugepage that is backing a VMA is. Shared memory segments are a little harder > but again, you can infer the information if you look around for long enough. > > However, this is awkward and not very user-friendly. With the patches (minus > MMUPageSize as I think we've agreed to postpone that), it's easy to see what > pagesize is being used at a glance. Without it, you need to know a fair bit > about hugepages are implemented in Linux to infer the information correctly. I agree completely. But, if we consider this a user ABI thing, then we're stuck with it for a long time, and we better make it flexible enough to at least contain the gunk we're planning on adding in a small number of years, like the fallback. We don't want to be adding this stuff if it isn't going to be stable. -- Dave