From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 6AAD76B0033 for ; Fri, 3 Feb 2017 22:09:45 -0500 (EST) Received: by mail-pf0-f200.google.com with SMTP id 80so44946225pfy.2 for ; Fri, 03 Feb 2017 19:09:45 -0800 (PST) Received: from out4441.biz.mail.alibaba.com (out4441.biz.mail.alibaba.com. [47.88.44.41]) by mx.google.com with ESMTP id y87si27166777pff.250.2017.02.03.19.09.42 for ; Fri, 03 Feb 2017 19:09:44 -0800 (PST) Reply-To: "Hillf Danton" From: "Hillf Danton" References: <20170203203222.gq7hk66yc36lpgtb@suse.de> In-Reply-To: <20170203203222.gq7hk66yc36lpgtb@suse.de> Subject: Re: [PATCH] mm, vmscan: Clear PGDAT_WRITEBACK when zone is balanced Date: Sat, 04 Feb 2017 11:09:27 +0800 Message-ID: <007701d27e94$18ea17e0$4abe47a0$@alibaba-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Language: zh-cn Sender: owner-linux-mm@kvack.org List-ID: To: 'Mel Gorman' , 'Andrew Morton' Cc: 'Johannes Weiner' , 'Michal Hocko' , 'Minchan Kim' , 'Rik van Riel' , linux-mm@kvack.org, linux-kernel@vger.kernel.org On February 04, 2017 4:32 AM Mel Gorman wrote: > > Hillf Danton pointed out that since commit 1d82de618dd ("mm, vmscan: > make kswapd reclaim in terms of nodes") that PGDAT_WRITEBACK is no longer > cleared. It was not noticed as triggering it requires pages under writeback > to cycle twice through the LRU and before kswapd gets stalled. Historically, > such issues tended to occur on small machines writing heavily to slow > storage such as a USB stick. Once kswapd stalls, direct reclaim stalls may > be higher but due to the fact that memory pressure is requires, it would not > be very noticable. Michal Hocko suggested removing the flag entirely but > the conservative fix is to restore the intended PGDAT_WRITEBACK behaviour > and clear the flag when a suitable zone is balanced. > > Signed-off-by: Mel Gorman > --- Acked-by: Hillf Danton > mm/vmscan.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 532a2a750952..3379fa5ce6d8 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3103,6 +3103,7 @@ static bool zone_balanced(struct zone *zone, int order, int classzone_idx) > */ > clear_bit(PGDAT_CONGESTED, &zone->zone_pgdat->flags); > clear_bit(PGDAT_DIRTY, &zone->zone_pgdat->flags); > + clear_bit(PGDAT_WRITEBACK, &zone->zone_pgdat->flags); > > return true; > } > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org