From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id D90B86B0078 for ; Tue, 12 Jan 2010 18:02:25 -0500 (EST) Date: Tue, 12 Jan 2010 15:01:52 -0800 From: Andrew Morton Subject: Re: [PATCH -mmotm-2010-01-06-14-34] check high watermark after shrink zone Message-Id: <20100112150152.78604b78.akpm@linux-foundation.org> In-Reply-To: <20100108141235.ef56b567.minchan.kim@barrios-desktop> References: <20100108141235.ef56b567.minchan.kim@barrios-desktop> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: KOSAKI Motohiro , Mel Gorman , Rik van Riel , linux-mm , lkml List-ID: On Fri, 8 Jan 2010 14:12:35 +0900 Minchan Kim wrote: > Kswapd check that zone have enough free by zone_water_mark. > If any zone doesn't have enough page, it set all_zones_ok to zero. > all_zone_ok makes kswapd retry not sleeping. > > I think the watermark check before shrink zone is pointless. > Kswapd try to shrink zone then the check is meaningul. > > This patch move the check after shrink zone. The changelog is rather hard to understand. I changed it to : Kswapd checks that zone has sufficient pages free via zone_watermark_ok(). : : If any zone doesn't have enough pages, we set all_zones_ok to zero. : !all_zone_ok makes kswapd retry rather than sleeping. : : I think the watermark check before shrink_zone() is pointless. Only after : kswapd has tried to shrink the zone is the check meaningful. : : Move the check to after the call to shrink_zone(). > Signed-off-by: Minchan Kim > CC: KOSAKI Motohiro > CC: Mel Gorman > CC: Rik van Riel > --- > mm/vmscan.c | 21 +++++++++++---------- > 1 files changed, 11 insertions(+), 10 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 885207a..b81adf8 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2057,9 +2057,6 @@ loop_again: > priority != DEF_PRIORITY) > continue; > > - if (!zone_watermark_ok(zone, order, > - high_wmark_pages(zone), end_zone, 0)) > - all_zones_ok = 0; This will make kswapd stop doing reclaim if all zones have zone_is_all_unreclaimable(): if (zone_is_all_unreclaimable(zone)) continue; This seems bad. > temp_priority[i] = priority; > sc.nr_scanned = 0; > note_zone_scanning_priority(zone, priority); > @@ -2099,13 +2096,17 @@ loop_again: > total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) > sc.may_writepage = 1; > > - /* > - * We are still under min water mark. it mean we have > - * GFP_ATOMIC allocation failure risk. Hurry up! > - */ > - if (!zone_watermark_ok(zone, order, min_wmark_pages(zone), > - end_zone, 0)) > - has_under_min_watermark_zone = 1; > + if (!zone_watermark_ok(zone, order, > + high_wmark_pages(zone), end_zone, 0)) { > + all_zones_ok = 0; > + /* > + * We are still under min water mark. it mean we have > + * GFP_ATOMIC allocation failure risk. Hurry up! > + */ > + if (!zone_watermark_ok(zone, order, min_wmark_pages(zone), > + end_zone, 0)) > + has_under_min_watermark_zone = 1; > + } > The vmscan.c code makes an effort to look nice in an 80-col display. -- 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