From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758434AbdACUo7 (ORCPT ); Tue, 3 Jan 2017 15:44:59 -0500 Received: from mx2.suse.de ([195.135.220.15]:53606 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757005AbdACUoz (ORCPT ); Tue, 3 Jan 2017 15:44:55 -0500 Date: Tue, 3 Jan 2017 21:43:33 +0100 From: Michal Hocko To: Vlastimil Babka Cc: linux-mm@kvack.org, Andrew Morton , Mel Gorman , Johannes Weiner , Rik van Riel , LKML Subject: Re: [PATCH 3/7] mm, vmscan: show the number of skipped pages in mm_vmscan_lru_isolate Message-ID: <20170103204331.GB13873@dhcp22.suse.cz> References: <20161228153032.10821-1-mhocko@kernel.org> <20161228153032.10821-4-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 03-01-17 18:21:48, Vlastimil Babka wrote: > On 12/28/2016 04:30 PM, Michal Hocko wrote: > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -1428,6 +1428,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, > > unsigned long nr_taken = 0; > > unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 }; > > unsigned long nr_skipped[MAX_NR_ZONES] = { 0, }; > > + unsigned long skipped = 0, total_skipped = 0; > > unsigned long scan, nr_pages; > > LIST_HEAD(pages_skipped); > > > > @@ -1479,14 +1480,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, > > */ > > if (!list_empty(&pages_skipped)) { > > int zid; > > - unsigned long total_skipped = 0; > > > > for (zid = 0; zid < MAX_NR_ZONES; zid++) { > > if (!nr_skipped[zid]) > > continue; > > > > __count_zid_vm_events(PGSCAN_SKIP, zid, nr_skipped[zid]); > > - total_skipped += nr_skipped[zid]; > > + skipped += nr_skipped[zid]; > > } > > > > /* > > @@ -1494,13 +1494,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan, > > * close to unreclaimable. If the LRU list is empty, account > > * skipped pages as a full scan. > > */ > > - scan += list_empty(src) ? total_skipped : total_skipped >> 2; > > + total_skipped = list_empty(src) ? skipped : skipped >> 2; > > Should the tracepoint output reflect this halving heuristic or rather report > the raw data? Or is each variant inferrable from the other? I would rather see the raw data because you can always go and check the _current_ implementation and calculate the heuristic. -- Michal Hocko SUSE Labs