From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752215AbcFLJjG (ORCPT ); Sun, 12 Jun 2016 05:39:06 -0400 Received: from out4133-50.mail.aliyun.com ([42.120.133.50]:9798 "EHLO out4133-50.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750724AbcFLJjE (ORCPT ); Sun, 12 Jun 2016 05:39:04 -0400 X-Greylist: delayed 320 seconds by postgrey-1.27 at vger.kernel.org; Sun, 12 Jun 2016 05:39:04 EDT X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R181e4;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e02c03294;MF=hillf.zj@alibaba-inc.com;NM=1;PH=DS;RN=3;SR=0;TI=SMTPD_----4uul9Dd_1465724004; Reply-To: "Hillf Danton" From: "Hillf Danton" To: "Mel Gorman" Cc: "linux-kernel" , References: <02fe01d1c48b$c44e9e80$4cebdb80$@alibaba-inc.com> In-Reply-To: <02fe01d1c48b$c44e9e80$4cebdb80$@alibaba-inc.com> Subject: Re: [PATCH 06/27] mm, vmscan: Make kswapd reclaim in terms of nodes Date: Sun, 12 Jun 2016 17:33:24 +0800 Message-ID: <02ff01d1c48d$78112f40$68338dc0$@alibaba-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQL4OBwvpazaJd0r1y5tK3X+cjnnfJ2Yp1Sg Content-Language: zh-cn Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > /* > - * kswapd shrinks the zone by the number of pages required to reach > - * the high watermark. > + * kswapd shrinks a node of pages that are at or below the highest usable > + * zone that is currently unbalanced. > * > * Returns true if kswapd scanned at least the requested number of pages to > * reclaim or if the lack of progress was due to pages under writeback. > * This is used to determine if the scanning priority needs to be raised. > */ > -static bool kswapd_shrink_zone(struct zone *zone, > +static bool kswapd_shrink_node(pg_data_t *pgdat, > int classzone_idx, > struct scan_control *sc) > { > - unsigned long balance_gap; > - bool lowmem_pressure; > - struct pglist_data *pgdat = zone->zone_pgdat; > + struct zone *zone; > + unsigned long nr_to_reclaim = 0; > + int z; > > - /* Reclaim above the high watermark. */ > - sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone)); > + /* Reclaim a number of pages proportional to the number of zones */ > + for (z = 0; z <= classzone_idx; z++) { > + zone = pgdat->node_zones + z; > + if (!populated_zone(zone)) > + continue; > > - /* > - * We put equal pressure on every zone, unless one zone has way too > - * many pages free already. The "too many pages" is defined as the > - * 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), DIV_ROUND_UP( > - zone->managed_pages, KSWAPD_ZONE_BALANCE_GAP_RATIO)); > + nr_to_reclaim += max(high_wmark_pages(zone), SWAP_CLUSTER_MAX); > + } Missing sc->nr_to_reclaim = nr_to_reclaim; ? > > /* > - * If there is no low memory pressure or the zone is balanced then no > - * reclaim is necessary > + * Historically care was taken to put equal pressure on all zones but > + * now pressure is applied based on node LRU order. > */ > - lowmem_pressure = (buffer_heads_over_limit && is_highmem(zone)); > - if (!lowmem_pressure && zone_balanced(zone, sc->order, false, > - balance_gap, classzone_idx)) > - return true; > - > - shrink_node(zone->zone_pgdat, sc, classzone_idx); > - > - /* TODO: ANOMALY */ > - clear_bit(PGDAT_WRITEBACK, &pgdat->flags); > + shrink_node(pgdat, sc, classzone_idx); > > /* > - * If a zone reaches its high watermark, consider it to be no longer > - * congested. It's possible there are dirty pages backed by congested > - * BDIs but as pressure is relieved, speculatively avoid congestion > - * waits. > + * Fragmentation may mean that the system cannot be rebalanced for > + * high-order allocations. If twice the allocation size has been > + * reclaimed then recheck watermarks only at order-0 to prevent > + * excessive reclaim. Assume that a process requested a high-order > + * can direct reclaim/compact. > */ > - if (pgdat_reclaimable(zone->zone_pgdat) && > - zone_balanced(zone, sc->order, false, 0, classzone_idx)) { > - clear_bit(PGDAT_CONGESTED, &pgdat->flags); > - clear_bit(PGDAT_DIRTY, &pgdat->flags); > - } > + if (sc->order && sc->nr_reclaimed >= 2UL << sc->order) > + sc->order = 0; > > return sc->nr_scanned >= sc->nr_to_reclaim; > }