From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1425115AbcFHM5b (ORCPT ); Wed, 8 Jun 2016 08:57:31 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:35926 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161222AbcFHM53 (ORCPT ); Wed, 8 Jun 2016 08:57:29 -0400 Date: Wed, 8 Jun 2016 14:57:27 +0200 From: Michal Hocko To: Johannes Weiner Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Rik van Riel , Mel Gorman , Andrea Arcangeli , Andi Kleen , Tim Chen , kernel-team@fb.com Subject: Re: [PATCH 08/10] mm: deactivations shouldn't bias the LRU balance Message-ID: <20160608125727.GI22570@dhcp22.suse.cz> References: <20160606194836.3624-1-hannes@cmpxchg.org> <20160606194836.3624-9-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160606194836.3624-9-hannes@cmpxchg.org> 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 Mon 06-06-16 15:48:34, Johannes Weiner wrote: > Operations like MADV_FREE, FADV_DONTNEED etc. currently move any > affected active pages to the inactive list to accelerate their reclaim > (good) but also steer page reclaim toward that LRU type, or away from > the other (bad). > > The reason why this is undesirable is that such operations are not > part of the regular page aging cycle, and rather a fluke that doesn't > say much about the remaining pages on that list. They might all be in > heavy use. But once the chunk of easy victims has been purged, the VM > continues to apply elevated pressure on the remaining hot pages. The > other LRU, meanwhile, might have easily reclaimable pages, and there > was never a need to steer away from it in the first place. > > As the previous patch outlined, we should focus on recording actually > observed cost to steer the balance rather than speculating about the > potential value of one LRU list over the other. In that spirit, leave > explicitely deactivated pages to the LRU algorithm to pick up, and let > rotations decide which list is the easiest to reclaim. > > Signed-off-by: Johannes Weiner Acked-by: Michal Hocko > --- > mm/swap.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/mm/swap.c b/mm/swap.c > index 645d21242324..ae07b469ddca 100644 > --- a/mm/swap.c > +++ b/mm/swap.c > @@ -538,7 +538,6 @@ static void lru_deactivate_file_fn(struct page *page, struct lruvec *lruvec, > > if (active) > __count_vm_event(PGDEACTIVATE); > - lru_note_cost(lruvec, !file, hpage_nr_pages(page)); > } > > > @@ -546,7 +545,6 @@ static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec, > void *arg) > { > if (PageLRU(page) && PageActive(page) && !PageUnevictable(page)) { > - int file = page_is_file_cache(page); > int lru = page_lru_base_type(page); > > del_page_from_lru_list(page, lruvec, lru + LRU_ACTIVE); > @@ -555,7 +553,6 @@ static void lru_deactivate_fn(struct page *page, struct lruvec *lruvec, > add_page_to_lru_list(page, lruvec, lru); > > __count_vm_event(PGDEACTIVATE); > - lru_note_cost(lruvec, !file, hpage_nr_pages(page)); > } > } > > -- > 2.8.3 -- Michal Hocko SUSE Labs