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Date: Tue, 5 Jul 2016 11:14:05 +0100
From: Mel Gorman <mgorman@...hsingularity.net>
To: Minchan Kim <minchan@...nel.org>
Cc: Michal Hocko <mhocko@...e.cz>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
Vlastimil Babka <vbabka@...e.cz>,
Johannes Weiner <hannes@...xchg.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/31] mm, vmscan: move LRU lists to node
On Tue, Jul 05, 2016 at 10:19:57AM +0900, Minchan Kim wrote:
> On Fri, Jul 01, 2016 at 09:01:11PM +0100, Mel Gorman wrote:
> > This moves the LRU lists from the zone to the node and related data such
> > as counters, tracing, congestion tracking and writeback tracking.
> > Unfortunately, due to reclaim and compaction retry logic, it is necessary
> > to account for the number of LRU pages on both zone and node logic. Most
> > reclaim logic is based on the node counters but the retry logic uses the
> > zone counters which do not distinguish inactive and inactive sizes. It
>
> active
>
Fixed.
> > @@ -352,12 +352,12 @@ static inline struct lruvec *mem_cgroup_zone_lruvec(struct zone *zone,
> > * we have to be prepared to initialize lruvec->zone here;
>
> lruvec->pgdat
>
Fixed.
> > @@ -357,13 +360,6 @@ struct zone {
> > #ifdef CONFIG_NUMA
> > int node;
> > #endif
> > -
> > - /*
> > - * The target ratio of ACTIVE_ANON to INACTIVE_ANON pages on
> > - * this zone's LRU. Maintained by the pageout code.
> > - */
> > - unsigned int inactive_ratio;
> > -
> > struct pglist_data *zone_pgdat;
> > struct per_cpu_pageset __percpu *pageset;
> >
> > @@ -495,9 +491,6 @@ struct zone {
> >
> > /* Write-intensive fields used by page reclaim */
>
> trivial:
> We moved lru_lock and lruvec to pgdat so I'm not sure we need ZONE_PADDING,
> still.
>
It still separates the page allocator structures from compaction and
vmstats. The comment is misleading so I added a patch to clarify what
the padding is doing.
> >
> > - /* Fields commonly accessed by the page reclaim scanner */
> > - struct lruvec lruvec;
> > -
> > /*
> > * When free pages are below this point, additional steps are taken
> > * when reading the number of free pages to avoid per-cpu counter
> > @@ -537,17 +530,20 @@ struct zone {
> >
> > enum zone_flags {
> > ZONE_RECLAIM_LOCKED, /* prevents concurrent reclaim */
> > - ZONE_CONGESTED, /* zone has many dirty pages backed by
> > + ZONE_FAIR_DEPLETED, /* fair zone policy batch depleted */
> > +};
> > +
>
> > +enum pgdat_flags {
> > + PGDAT_CONGESTED, /* zone has many dirty pages backed by
>
> node or pgdat, whatever.
>
Fixed.
> > * a congested BDI
> > */
> > - ZONE_DIRTY, /* reclaim scanning has recently found
> > + PGDAT_DIRTY, /* reclaim scanning has recently found
> > * many dirty file pages at the tail
> > * of the LRU.
> > */
> > - ZONE_WRITEBACK, /* reclaim scanning has recently found
> > + PGDAT_WRITEBACK, /* reclaim scanning has recently found
> > * many pages under writeback
> > */
> > - ZONE_FAIR_DEPLETED, /* fair zone policy batch depleted */
> > };
> >
> > static inline unsigned long zone_end_pfn(const struct zone *zone)
> > @@ -701,12 +697,26 @@ typedef struct pglist_data {
> > unsigned long first_deferred_pfn;
> > #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
> >
> > +
>
> Unnecessary change.
>
Fixed.
> > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
> > index d1744aa3ab9c..ced0c3e9da88 100644
> > --- a/include/linux/vmstat.h
> > +++ b/include/linux/vmstat.h
> > @@ -178,6 +178,23 @@ static inline unsigned long zone_page_state_snapshot(struct zone *zone,
> > return x;
> > }
> >
> > +static inline unsigned long node_page_state_snapshot(pg_data_t *pgdat,
> > + enum zone_stat_item item)
>
> enum node_stat_item
>
Fixed
> > @@ -1147,9 +1147,9 @@ static void free_one_page(struct zone *zone,
> > {
> > unsigned long nr_scanned;
> > spin_lock(&zone->lock);
> > - nr_scanned = zone_page_state(zone, NR_PAGES_SCANNED);
> > + nr_scanned = node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED);
> > if (nr_scanned)
> > - __mod_zone_page_state(zone, NR_PAGES_SCANNED, -nr_scanned);
> > + __mod_node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED, -nr_scanned);
> >
> > if (unlikely(has_isolate_pageblock(zone) ||
> > is_migrate_isolate(migratetype))) {
> > @@ -3526,7 +3526,7 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order,
> >
> > available = reclaimable = zone_reclaimable_pages(zone);
> > available -= DIV_ROUND_UP(no_progress_loops * available,
> > - MAX_RECLAIM_RETRIES);
> > + MAX_RECLAIM_RETRIES);
>
> Unnecessary change.
>
Fixed.
> > available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
> >
> > /*
> > @@ -4331,6 +4331,7 @@ void show_free_areas(unsigned int filter)
>
> <snip.
>
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index e7ffcd259cc4..86a523a761c9 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -191,26 +191,42 @@ static bool sane_reclaim(struct scan_control *sc)
> > }
> > #endif
> >
> > +/*
> > + * This misses isolated pages which are not accounted for to save counters.
> > + * As the data only determines if reclaim or compaction continues, it is
> > + * not expected that isolated pages will be a dominating factor.
>
> When I read below commit, one of the reason it was introduced is whether we
> should continue to reclaim page or not.
> At that time, several people wanted it by my guessing [suggested|acked]-by
> so I think we should notice it to them.
>
> Michal?
>
Ultimately this gets fixed up at the end of the series when
zone_reclaimable_pages gets removed again to avoid double accounting.
--
Mel Gorman
SUSE Labs
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