From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f54.google.com (mail-pb0-f54.google.com [209.85.160.54]) by kanga.kvack.org (Postfix) with ESMTP id 710F86B0036 for ; Mon, 19 May 2014 00:09:20 -0400 (EDT) Received: by mail-pb0-f54.google.com with SMTP id jt11so5238918pbb.41 for ; Sun, 18 May 2014 21:09:19 -0700 (PDT) Received: from mail-pa0-x22d.google.com (mail-pa0-x22d.google.com [2607:f8b0:400e:c03::22d]) by mx.google.com with ESMTPS id xg6si17858987pab.9.2014.05.18.21.09.19 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 18 May 2014 21:09:19 -0700 (PDT) Received: by mail-pa0-f45.google.com with SMTP id ey11so5173716pad.4 for ; Sun, 18 May 2014 21:09:19 -0700 (PDT) From: Jianyu Zhan Subject: [PATCH] mm/vmscan.c: use DIV_ROUND_UP for calculation of zone's balance_gap and correct comments. Date: Mon, 19 May 2014 12:08:30 +0800 Message-Id: <1400472510-24375-1-git-send-email-nasa4836@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org, hannes@cmpxchg.org, shli@kernel.org, minchan@kernel.org, riel@redhat.com, nasa4836@gmail.com, mgorman@suse.de, cmetcalf@tilera.com, aquini@redhat.com, mhocko@suse.cz, vdavydov@parallels.com, glommer@openvz.org, dchinner@redhat.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org Currently, we use (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / KSWAPD_ZONE_BALANCE_GAP_RATIO to avoid a zero gap value. It's better to use DIV_ROUND_UP macro for neater code and clear meaning. Besides, the gap value is calculated against the per-zone "managed pages", not "present pages". This patch also corrects the comment and do some rephrasing. Signed-off-by: Jianyu Zhan --- include/linux/swap.h | 8 ++++---- mm/vmscan.c | 10 ++++------ 2 files changed, 8 insertions(+), 10 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 5a14b92..58e1696 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -166,10 +166,10 @@ enum { #define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX /* - * Ratio between the present memory in the zone and the "gap" that - * we're allowing kswapd to shrink in addition to the per-zone high - * wmark, even for zones that already have the high wmark satisfied, - * in order to provide better per-zone lru behavior. We are ok to + * Ratio between zone->managed_pages and the "gap" that above the per-zone + * "high_wmark". While balancing nodes, We allow kswapd to shrink zones that + * do not meet the (high_wmark + gap) watermark, even which already met the + * high_wmark, in order to provide better per-zone lru behavior. We are ok to * spend not more than 1% of the memory for this zone balancing "gap". */ #define KSWAPD_ZONE_BALANCE_GAP_RATIO 100 diff --git a/mm/vmscan.c b/mm/vmscan.c index 32c661d..9ef9f6c 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2268,9 +2268,8 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) * there is a buffer of free pages available to give compaction * a reasonable chance of completing and allocating the page */ - balance_gap = min(low_wmark_pages(zone), - (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / - KSWAPD_ZONE_BALANCE_GAP_RATIO); + balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP( + zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO)); watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order); watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0); @@ -2891,9 +2890,8 @@ static bool kswapd_shrink_zone(struct zone *zone, * high wmark plus a "gap" where the gap is either the low * watermark or 1% of the zone, whichever is smaller. */ - balance_gap = min(low_wmark_pages(zone), - (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / - KSWAPD_ZONE_BALANCE_GAP_RATIO); + balance_gap = min(low_wmark_pages(zone), DIV_ROUND_UP( + zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO)); /* * If there is no low memory pressure or the zone is balanced then no -- 2.0.0-rc3 -- 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