From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750862AbdALVMb (ORCPT ); Thu, 12 Jan 2017 16:12:31 -0500 Received: from mail-wm0-f65.google.com ([74.125.82.65]:35537 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750733AbdALVMa (ORCPT ); Thu, 12 Jan 2017 16:12:30 -0500 From: Michal Hocko To: Andrew Morton Cc: Vlastimil Babka , Hugh Dickins , Johannes Weiner , Mel Gorman , , LKML , Michal Hocko Subject: [PATCH] mm, vmscan: do not count freed pages as PGDEACTIVATE Date: Thu, 12 Jan 2017 22:12:21 +0100 Message-Id: <20170112211221.17636-1-mhocko@kernel.org> X-Mailer: git-send-email 2.11.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michal Hocko PGDEACTIVATE represents the number of pages moved from the active list to the inactive list. At least this sounds like the original motivation of the counter. move_active_pages_to_lru, however, counts pages which got freed in the mean time as deactivated as well. This is a very rare event and counting them as deactivation in itself is not harmful but it makes the code more convoluted than necessary - we have to count both all pages and those which are freed which is a bit confusing. After this patch the PGDEACTIVATE should have a slightly more clear semantic and only count those pages which are moved from the active to the inactive list which is a plus. Suggested-by: Vlastimil Babka Signed-off-by: Michal Hocko --- Hi, Vlastimil has pointed out [1] that move_active_pages_to_lru is more confusing than necessary because we count two things, pgmoved and nr_moved. I believe that counting freed pages as PGDEACTIVATE is more confusing than helpful. I doubt that this patch will make any real difference in the real life but it at least makes the code easier which is a plus so I think this is more a cleanup than any bug fix. [1] http://lkml.kernel.org/r/646c3551-e794-611c-5247-490bd89133db@suse.cz mm/vmscan.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index cf940af609fd..7e1c3cd91fab 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1878,7 +1878,6 @@ static unsigned move_active_pages_to_lru(struct lruvec *lruvec, enum lru_list lru) { struct pglist_data *pgdat = lruvec_pgdat(lruvec); - unsigned long pgmoved = 0; struct page *page; int nr_pages; int nr_moved = 0; @@ -1893,7 +1892,6 @@ static unsigned move_active_pages_to_lru(struct lruvec *lruvec, nr_pages = hpage_nr_pages(page); update_lru_size(lruvec, lru, page_zonenum(page), nr_pages); list_move(&page->lru, &lruvec->lists[lru]); - pgmoved += nr_pages; if (put_page_testzero(page)) { __ClearPageLRU(page); @@ -1913,7 +1911,7 @@ static unsigned move_active_pages_to_lru(struct lruvec *lruvec, } if (!is_active_lru(lru)) - __count_vm_events(PGDEACTIVATE, pgmoved); + __count_vm_events(PGDEACTIVATE, nr_moved); return nr_moved; } -- 2.11.0