From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751542AbcGMKAY (ORCPT ); Wed, 13 Jul 2016 06:00:24 -0400 Received: from outbound-smtp11.blacknight.com ([46.22.139.16]:53662 "EHLO outbound-smtp11.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750739AbcGMKAP (ORCPT ); Wed, 13 Jul 2016 06:00:15 -0400 From: Mel Gorman To: Andrew Morton , Linux-MM Cc: Johannes Weiner , Minchan Kim , LKML , Mel Gorman Subject: [PATCH 1/4] mm, vmscan: Have kswapd reclaim from all zones if reclaiming and buffer_heads_over_limit -fix Date: Wed, 13 Jul 2016 11:00:01 +0100 Message-Id: <1468404004-5085-2-git-send-email-mgorman@techsingularity.net> X-Mailer: git-send-email 2.6.4 In-Reply-To: <1468404004-5085-1-git-send-email-mgorman@techsingularity.net> References: <1468404004-5085-1-git-send-email-mgorman@techsingularity.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Johannes reported that the comment about buffer_heads_over_limit in balance_pgdat only made sense in the context of the patch. This patch clarifies the reasoning and how it applies to 32 and 64 bit systems. This is a fix to the mmotm patch mm-vmscan-have-kswapd-reclaim-from-all-zones-if-reclaiming-and-buffer_heads_over_limit.patch Suggested-by: Johannes Weiner Signed-off-by: Mel Gorman --- mm/vmscan.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index d079210d46ee..21eae17ee730 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3131,12 +3131,13 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx) /* * If the number of buffer_heads exceeds the maximum allowed - * then consider reclaiming from all zones. This is not - * specific to highmem which may not exist but it is it is - * expected that buffer_heads are stripped in writeback. - * Reclaim may still not go ahead if all eligible zones - * for the original allocation request are balanced to - * avoid excessive reclaim from kswapd. + * then consider reclaiming from all zones. This has a dual + * purpose -- on 64-bit systems it is expected that + * buffer_heads are stripped during active rotation. On 32-bit + * systems, highmem pages can pin lowmem memory and shrinking + * buffers can relieve lowmem pressure. Reclaim may still not + * go ahead if all eligible zones for the original allocation + * request are balanced to avoid excessive reclaim from kswapd. */ if (buffer_heads_over_limit) { for (i = MAX_NR_ZONES - 1; i >= 0; i--) { -- 2.6.4