From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755507AbYLECx1 (ORCPT ); Thu, 4 Dec 2008 21:53:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751428AbYLECxS (ORCPT ); Thu, 4 Dec 2008 21:53:18 -0500 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:42608 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750839AbYLECxS (ORCPT ); Thu, 4 Dec 2008 21:53:18 -0500 From: KOSAKI Motohiro To: Nick Piggin , wassim dagash Subject: Re: KSWAPD Algorithm - 100% CPU Cc: kosaki.motohiro@jp.fujitsu.com, linux-kernel@vger.kernel.org, Andrew Morton In-Reply-To: <20081204140200.GA22631@wotan.suse.de> References: <20081203163740.1D4D.KOSAKI.MOTOHIRO@jp.fujitsu.com> <20081204140200.GA22631@wotan.suse.de> Message-Id: <20081205095905.1D83.KOSAKI.MOTOHIRO@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.42 [ja] Date: Fri, 5 Dec 2008 11:53:13 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > kswapd_max_order check and reset should probably go inside > balance_pgdat:loop_again loop. > > It is possible we could have a kswapd_max_order[MAX_NR_ZONES] or > something, but I don't know if the complexity would be worth while > given that huge order allocations aren't too common, and resetting > kswapd_max_order inside the loop should be a reasonable fix. It seems excellent. wassim, Could you please test this patch? == From: KOSAKI Motohiro Subject: [PATCH] kswapd: add infinite loop stopper Wassim Dagash reported following kswapd infinite loop problem. kswapd runs in some infinite loop trying to swap until order 10 of zone highmem is OK, While zone higmem (as I understand) has nothing to do with contiguous memory (cause there is no 1-1 mapping) which means kswapd will continue to try to balance order 10 of zone highmem forever (or until someone release a very large chunk of highmem). He proposed remove contenious checking on highmem at all. However hugepage on highmem need contenious highmem page. To add infinite loop stopper is simple and good. Reported-by: wassim dagash Signed-off-by: KOSAKI Motohiro --- mm/vmscan.c | 10 ++++++++++ 1 file changed, 10 insertions(+) Index: b/mm/vmscan.c =================================================================== --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1921,6 +1921,16 @@ out: try_to_freeze(); + /* + When highmem is very fragmented, + alloc_pages(GFP_KERNEL, very-high-order) can cause + infinite loop because zone_watermark_ok(highmem) failed. + However, (alloc_pages(GFP_KERNEL..) indicate highmem memory + continuousness isn't necessary. + Therefore 2nd loop or after stop contenious check. + */ + order = sc->order = 0; + goto loop_again; }