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Date: Wed, 1 Mar 2017 16:41:07 +0100
From: Michal Hocko <mhocko@...nel.org>
To: Johannes Weiner <hannes@...xchg.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Jia He <hejianet@...il.com>, Mel Gorman <mgorman@...e.de>,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
kernel-team@...com
Subject: Re: [PATCH 7/9] mm: delete NR_PAGES_SCANNED and pgdat_reclaimable()
On Tue 28-02-17 16:40:05, Johannes Weiner wrote:
> NR_PAGES_SCANNED counts number of pages scanned since the last page
> free event in the allocator. This was used primarily to measure the
> reclaimability of zones and nodes, and determine when reclaim should
> give up on them. In that role, it has been replaced in the preceeding
> patches by a different mechanism.
>
> Being implemented as an efficient vmstat counter, it was automatically
> exported to userspace as well. It's however unlikely that anyone
> outside the kernel is using this counter in any meaningful way.
>
> Remove the counter and the unused pgdat_reclaimable().
\o/
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
Acked-by: Michal Hocko <mhocko@...e.com>
> ---
> include/linux/mmzone.h | 1 -
> mm/internal.h | 1 -
> mm/page_alloc.c | 15 +++------------
> mm/vmscan.c | 9 ---------
> mm/vmstat.c | 22 +++-------------------
> 5 files changed, 6 insertions(+), 42 deletions(-)
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index d2c50ab6ae40..04e0969966f6 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -149,7 +149,6 @@ enum node_stat_item {
> NR_UNEVICTABLE, /* " " " " " */
> NR_ISOLATED_ANON, /* Temporary isolated pages from anon lru */
> NR_ISOLATED_FILE, /* Temporary isolated pages from file lru */
> - NR_PAGES_SCANNED, /* pages scanned since last reclaim */
> WORKINGSET_REFAULT,
> WORKINGSET_ACTIVATE,
> WORKINGSET_NODERECLAIM,
> diff --git a/mm/internal.h b/mm/internal.h
> index aae93e3fd984..c583ce1b32b9 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -91,7 +91,6 @@ extern unsigned long highest_memmap_pfn;
> */
> extern int isolate_lru_page(struct page *page);
> extern void putback_lru_page(struct page *page);
> -extern bool pgdat_reclaimable(struct pglist_data *pgdat);
>
> /*
> * in mm/rmap.c:
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index f50e36e7b024..9ac639864bed 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1088,15 +1088,11 @@ static void free_pcppages_bulk(struct zone *zone, int count,
> {
> int migratetype = 0;
> int batch_free = 0;
> - unsigned long nr_scanned, flags;
> + unsigned long flags;
> bool isolated_pageblocks;
>
> spin_lock_irqsave(&zone->lock, flags);
> isolated_pageblocks = has_isolate_pageblock(zone);
> - nr_scanned = node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED);
> - if (nr_scanned)
> - __mod_node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED, -nr_scanned);
> -
> while (count) {
> struct page *page;
> struct list_head *list;
> @@ -1148,13 +1144,10 @@ static void free_one_page(struct zone *zone,
> unsigned int order,
> int migratetype)
> {
> - unsigned long nr_scanned, flags;
> + unsigned long flags;
> +
> spin_lock_irqsave(&zone->lock, flags);
> __count_vm_events(PGFREE, 1 << order);
> - nr_scanned = node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED);
> - if (nr_scanned)
> - __mod_node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED, -nr_scanned);
> -
> if (unlikely(has_isolate_pageblock(zone) ||
> is_migrate_isolate(migratetype))) {
> migratetype = get_pfnblock_migratetype(page, pfn);
> @@ -4497,7 +4490,6 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
> #endif
> " writeback_tmp:%lukB"
> " unstable:%lukB"
> - " pages_scanned:%lu"
> " all_unreclaimable? %s"
> "\n",
> pgdat->node_id,
> @@ -4520,7 +4512,6 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
> K(node_page_state(pgdat, NR_SHMEM)),
> K(node_page_state(pgdat, NR_WRITEBACK_TEMP)),
> K(node_page_state(pgdat, NR_UNSTABLE_NFS)),
> - node_page_state(pgdat, NR_PAGES_SCANNED),
> pgdat->kswapd_failures >= MAX_RECLAIM_RETRIES ?
> "yes" : "no");
> }
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 8cff6e2cd02c..35b791a8922b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -229,12 +229,6 @@ unsigned long pgdat_reclaimable_pages(struct pglist_data *pgdat)
> return nr;
> }
>
> -bool pgdat_reclaimable(struct pglist_data *pgdat)
> -{
> - return node_page_state_snapshot(pgdat, NR_PAGES_SCANNED) <
> - pgdat_reclaimable_pages(pgdat) * 6;
> -}
> -
> /**
> * lruvec_lru_size - Returns the number of pages on the given LRU list.
> * @lruvec: lru vector
> @@ -1749,7 +1743,6 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
> reclaim_stat->recent_scanned[file] += nr_taken;
>
> if (global_reclaim(sc)) {
> - __mod_node_page_state(pgdat, NR_PAGES_SCANNED, nr_scanned);
> if (current_is_kswapd())
> __count_vm_events(PGSCAN_KSWAPD, nr_scanned);
> else
> @@ -1952,8 +1945,6 @@ static void shrink_active_list(unsigned long nr_to_scan,
> __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
> reclaim_stat->recent_scanned[file] += nr_taken;
>
> - if (global_reclaim(sc))
> - __mod_node_page_state(pgdat, NR_PAGES_SCANNED, nr_scanned);
> __count_vm_events(PGREFILL, nr_scanned);
>
> spin_unlock_irq(&pgdat->lru_lock);
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index ff16cdc15df2..eface7467ea5 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -954,7 +954,6 @@ const char * const vmstat_text[] = {
> "nr_unevictable",
> "nr_isolated_anon",
> "nr_isolated_file",
> - "nr_pages_scanned",
> "workingset_refault",
> "workingset_activate",
> "workingset_nodereclaim",
> @@ -1375,7 +1374,6 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
> "\n min %lu"
> "\n low %lu"
> "\n high %lu"
> - "\n node_scanned %lu"
> "\n spanned %lu"
> "\n present %lu"
> "\n managed %lu",
> @@ -1383,7 +1381,6 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
> min_wmark_pages(zone),
> low_wmark_pages(zone),
> high_wmark_pages(zone),
> - node_page_state(zone->zone_pgdat, NR_PAGES_SCANNED),
> zone->spanned_pages,
> zone->present_pages,
> zone->managed_pages);
> @@ -1584,22 +1581,9 @@ int vmstat_refresh(struct ctl_table *table, int write,
> for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++) {
> val = atomic_long_read(&vm_zone_stat[i]);
> if (val < 0) {
> - switch (i) {
> - case NR_PAGES_SCANNED:
> - /*
> - * This is often seen to go negative in
> - * recent kernels, but not to go permanently
> - * negative. Whilst it would be nicer not to
> - * have exceptions, rooting them out would be
> - * another task, of rather low priority.
> - */
> - break;
> - default:
> - pr_warn("%s: %s %ld\n",
> - __func__, vmstat_text[i], val);
> - err = -EINVAL;
> - break;
> - }
> + pr_warn("%s: %s %ld\n",
> + __func__, vmstat_text[i], val);
> + err = -EINVAL;
> }
> }
> if (err)
> --
> 2.11.1
--
Michal Hocko
SUSE Labs
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