From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751832AbcGNBKK (ORCPT ); Wed, 13 Jul 2016 21:10:10 -0400 Received: from LGEAMRELO12.lge.com ([156.147.23.52]:50387 "EHLO lgeamrelo12.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751526AbcGNBKE (ORCPT ); Wed, 13 Jul 2016 21:10:04 -0400 X-Original-SENDERIP: 156.147.1.125 X-Original-MAILFROM: minchan@kernel.org X-Original-SENDERIP: 165.244.98.204 X-Original-MAILFROM: minchan@kernel.org X-Original-SENDERIP: 10.177.223.161 X-Original-MAILFROM: minchan@kernel.org Date: Thu, 14 Jul 2016 10:11:19 +0900 From: Minchan Kim To: Mel Gorman CC: Andrew Morton , , Subject: Re: [PATCH] mm: fix pgalloc_stall on unpopulated zone Message-ID: <20160714011119.GA23512@bbox> References: <1468376653-26561-1-git-send-email-minchan@kernel.org> <20160713092504.GJ11400@suse.de> MIME-Version: 1.0 In-Reply-To: <20160713092504.GJ11400@suse.de> User-Agent: Mutt/1.5.21 (2010-09-15) X-MIMETrack: Itemize by SMTP Server on LGEKRMHUB06/LGE/LG Group(Release 8.5.3FP6|November 21, 2013) at 2016/07/14 10:10:01, Serialize by Router on LGEKRMHUB06/LGE/LG Group(Release 8.5.3FP6|November 21, 2013) at 2016/07/14 10:10:01, Serialize complete at 2016/07/14 10:10:01 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 13, 2016 at 10:25:04AM +0100, Mel Gorman wrote: > On Wed, Jul 13, 2016 at 11:24:13AM +0900, Minchan Kim wrote: > > If we use sc->reclaim_idx for accounting pgstall, it can increase > > the count on unpopulated zone, for example, movable zone(but > > my system doesn't have movable zone) if allocation request were > > GFP_HIGHUSER_MOVABLE. It doesn't make no sense. > > > > I wanted to track the highest zone allowed by each allocation regardless > of what the zone population state was. Otherwise, consider the following > on a NUMA system > > 1. An allocation request arrives for GFP_HIGHUSER_MOVABLE that stalls > 2. System has two nodes, node 0 with ZONE_NORMAL, node 1 with ZONE_HIGHMEM > 3. If the allocating process is on node 0, the stall is accounted on ZONE_NORMAL > 4. If the allocatinn process is on node 1, the stall is accounted on ZONE_HIGHMEM > > Multiple runs of the same workload on the same machine will see stall > statistics on different zones and renders the stat useless. This is > difficult to analyse because stalls accounted for on ZONE_NORMAL may or > may not be zone-constrained allocations. Fair enough. For the allocstall, it would be better to show the requested zone. > > The patch means that the vmstat accounting and tracepoint data is also > out of sync. One thing I wanted to be able to do was > > 1. Observe that there are alloc stalls on DMA32 or some other low zone > 2. Activate mm_vmscan_direct_reclaim_begin, filter on classzone_idx == > DMA32 and identify the source of the lowmem allocations > > If your patch is applied, I cannot depend on the stall stats any more > and the tracepoint is required to determine if there really any > zone-contrained allocations. It can be *inferred* from the skip stats > but only if such skips occurred and that is not guaranteed. Just a nit: Hmm, can't we omit classzone_idx in mm_vm_scan_direct_begin_template? Because every functions already have gfp_flags so that we can classzone_idx via gfp_zone(gfp_flags) without passing it. > > -- > Mel Gorman > SUSE Labs