Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932313AbaDVL5h (ORCPT ); Tue, 22 Apr 2014 07:57:37 -0400 Received: from e06smtp17.uk.ibm.com ([195.75.94.113]:52235 "EHLO e06smtp17.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932168AbaDVL5c (ORCPT ); Tue, 22 Apr 2014 07:57:32 -0400 Message-ID: <53565922.1050709@de.ibm.com> Date: Tue, 22 Apr 2014 13:57:22 +0200 From: Christian Borntraeger User-Agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Johannes Weiner CC: Rafael Aquini , Rik van Riel , Mel Gorman , Hugh Dickins , Suleiman Souhlal , stable@kernel.org, Andrew Morton , Linux Kernel Mailing List , Christian Ehrhardt , KVM list Subject: Re: commit 0bf1457f0cfca7b " mm: vmscan: do not swap anon pages just because free+file is low" causes heavy performance regression on paging References: <53564AA9.3060905@de.ibm.com> In-Reply-To: <53564AA9.3060905@de.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14042211-0542-0000-0000-000008BC0501 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/04/14 12:55, Christian Borntraeger wrote: > While preparing/testing some KVM on s390 patches for the next merge window (target is kvm/next which is based on 3.15-rc1) I faced a very severe performance hickup on guest paging (all anonymous memory). > > All memory bound guests are in "D" state now and the system is barely unusable. > > Reverting commit 0bf1457f0cfca7bc026a82323ad34bcf58ad035d > "mm: vmscan: do not swap anon pages just because free+file is low" makes the problem go away. > > According to /proc/vmstat the system is now in direct reclaim almost all the time for every page fault (more than 10x more direct reclaims than kswap reclaims) > With the patch being reverted everything is fine again. > > Any ideas? Here is an idea to tackle my problem and the original problem: reverting 0bf1457f0cfca7bc026a82323ad34bcf58ad035d + checking against low, also seems to make my system usable. --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1923,7 +1923,7 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, */ if (global_reclaim(sc)) { free = zone_page_state(zone, NR_FREE_PAGES); - if (unlikely(file + free <= high_wmark_pages(zone))) { + if (unlikely(file + free <= low_wmark_pages(zone))) { scan_balance = SCAN_ANON; goto out; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/