From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755295Ab0C3Hbx (ORCPT ); Tue, 30 Mar 2010 03:31:53 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:50314 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755225Ab0C3Hbr (ORCPT ); Tue, 30 Mar 2010 03:31:47 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Shaohua Li Subject: Re: [PATCH]vmscan: handle underflow for get_scan_ratio Cc: kosaki.motohiro@jp.fujitsu.com, "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "Wu, Fengguang" In-Reply-To: <20100330065358.GA24828@sli10-desk.sh.intel.com> References: <20100330153750.8EA2.A69D9226@jp.fujitsu.com> <20100330065358.GA24828@sli10-desk.sh.intel.com> Message-Id: <20100330160820.8EA8.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Tue, 30 Mar 2010 16:31:40 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > > > Very unfortunately, this patch isn't acceptable. In past time, vmscan > > > > had similar logic, but 1% swap-out made lots bug reports. > > > can you elaborate this? > > > Completely restore previous behavior (do full scan with priority 0) is > > > ok too. > > > > This is a option. but we need to know the root cause anyway. > I thought I mentioned the root cause in first mail. My debug shows > recent_rotated[0] is big, but recent_rotated[1] is almost zero, which makes > percent[0] 0. But you can double check too. To revert can save percent[0]==0 && priority==0 case. but it shouldn't happen, I think. It mean to happen big latency issue. Can you please try following patch? Also, I'll prepare reproduce environment soon. --- mm/vmscan.c | 12 ++++++++---- 1 files changed, 8 insertions(+), 4 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 79c8098..abf7f79 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1571,15 +1571,19 @@ static void get_scan_ratio(struct zone *zone, struct scan_control *sc, */ if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { spin_lock_irq(&zone->lru_lock); - reclaim_stat->recent_scanned[0] /= 2; - reclaim_stat->recent_rotated[0] /= 2; + while (reclaim_stat->recent_scanned[0] > anon / 4) { + reclaim_stat->recent_scanned[0] /= 2; + reclaim_stat->recent_rotated[0] /= 2; + } spin_unlock_irq(&zone->lru_lock); } if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { spin_lock_irq(&zone->lru_lock); - reclaim_stat->recent_scanned[1] /= 2; - reclaim_stat->recent_rotated[1] /= 2; + while (reclaim_stat->recent_scanned[1] > file / 4) { + reclaim_stat->recent_scanned[1] /= 2; + reclaim_stat->recent_rotated[1] /= 2; + } spin_unlock_irq(&zone->lru_lock); } -- 1.6.5.2