Re: [PATCH V2 5/7] mm: add vmstat account for MADV_FREE pages

[Michal Hocko]

On Fri 03-02-17 15:33:21, Shaohua Li wrote:
> Show MADV_FREE pages info in proc/sysfs files.

How are we going to use this information? Why it isn't sufficient to
watch for lazyfree events? I mean this adds quite some code and it is
not clear (at least from the changelog) we we need this information.

> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Shaohua Li <shli@xxxxxx>
> ---
>  drivers/base/node.c       |  2 ++
>  fs/proc/meminfo.c         |  1 +
>  include/linux/mm_inline.h | 31 ++++++++++++++++++++++++++++---
>  include/linux/mmzone.h    |  2 ++
>  mm/page_alloc.c           |  7 +++++--
>  mm/vmscan.c               |  9 +++++++--
>  mm/vmstat.c               |  2 ++
>  7 files changed, 47 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 5548f96..9138db8 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -71,6 +71,7 @@ static ssize_t node_read_meminfo(struct device *dev,
>  		       "Node %d Active(file):   %8lu kB\n"
>  		       "Node %d Inactive(file): %8lu kB\n"
>  		       "Node %d Unevictable:    %8lu kB\n"
> +		       "Node %d LazyFree:       %8lu kB\n"
>  		       "Node %d Mlocked:        %8lu kB\n",
>  		       nid, K(i.totalram),
>  		       nid, K(i.freeram),
> @@ -84,6 +85,7 @@ static ssize_t node_read_meminfo(struct device *dev,
>  		       nid, K(node_page_state(pgdat, NR_ACTIVE_FILE)),
>  		       nid, K(node_page_state(pgdat, NR_INACTIVE_FILE)),
>  		       nid, K(node_page_state(pgdat, NR_UNEVICTABLE)),
> +		       nid, K(node_page_state(pgdat, NR_LAZYFREE)),
>  		       nid, K(sum_zone_node_page_state(nid, NR_MLOCK)));
>  
>  #ifdef CONFIG_HIGHMEM
> diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
> index 8a42849..b2e7b31 100644
> --- a/fs/proc/meminfo.c
> +++ b/fs/proc/meminfo.c
> @@ -80,6 +80,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>  	show_val_kb(m, "Active(file):   ", pages[LRU_ACTIVE_FILE]);
>  	show_val_kb(m, "Inactive(file): ", pages[LRU_INACTIVE_FILE]);
>  	show_val_kb(m, "Unevictable:    ", pages[LRU_UNEVICTABLE]);
> +	show_val_kb(m, "LazyFree:       ", global_node_page_state(NR_LAZYFREE));
>  	show_val_kb(m, "Mlocked:        ", global_page_state(NR_MLOCK));
>  
>  #ifdef CONFIG_HIGHMEM
> diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
> index fdded06..3e496de 100644
> --- a/include/linux/mm_inline.h
> +++ b/include/linux/mm_inline.h
> @@ -48,25 +48,50 @@ static __always_inline void update_lru_size(struct lruvec *lruvec,
>  #endif
>  }
>  
> +static __always_inline void __update_lazyfree_size(struct lruvec *lruvec,
> +				enum zone_type zid, int nr_pages)
> +{
> +	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
> +
> +	__mod_node_page_state(pgdat, NR_LAZYFREE, nr_pages);
> +	__mod_zone_page_state(&pgdat->node_zones[zid], NR_ZONE_LAZYFREE,
> +				nr_pages);
> +}
> +
>  static __always_inline void add_page_to_lru_list(struct page *page,
>  				struct lruvec *lruvec, enum lru_list lru)
>  {
> -	update_lru_size(lruvec, lru, page_zonenum(page), hpage_nr_pages(page));
> +	enum zone_type zid = page_zonenum(page);
> +	int nr_pages = hpage_nr_pages(page);
> +
> +	if (lru == LRU_INACTIVE_FILE && page_is_lazyfree(page))
> +		__update_lazyfree_size(lruvec, zid, nr_pages);
> +	update_lru_size(lruvec, lru, zid, nr_pages);
>  	list_add(&page->lru, &lruvec->lists[lru]);
>  }
>  
>  static __always_inline void add_page_to_lru_list_tail(struct page *page,
>  				struct lruvec *lruvec, enum lru_list lru)
>  {
> -	update_lru_size(lruvec, lru, page_zonenum(page), hpage_nr_pages(page));
> +	enum zone_type zid = page_zonenum(page);
> +	int nr_pages = hpage_nr_pages(page);
> +
> +	if (lru == LRU_INACTIVE_FILE && page_is_lazyfree(page))
> +		__update_lazyfree_size(lruvec, zid, nr_pages);
> +	update_lru_size(lruvec, lru, zid, nr_pages);
>  	list_add_tail(&page->lru, &lruvec->lists[lru]);
>  }
>  
>  static __always_inline void del_page_from_lru_list(struct page *page,
>  				struct lruvec *lruvec, enum lru_list lru)
>  {
> +	enum zone_type zid = page_zonenum(page);
> +	int nr_pages = hpage_nr_pages(page);
> +
>  	list_del(&page->lru);
> -	update_lru_size(lruvec, lru, page_zonenum(page), -hpage_nr_pages(page));
> +	if (lru == LRU_INACTIVE_FILE && page_is_lazyfree(page))
> +		__update_lazyfree_size(lruvec, zid, -nr_pages);
> +	update_lru_size(lruvec, lru, zid, -nr_pages);
>  }
>  
>  /**
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 338a786a..78985f1 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -118,6 +118,7 @@ enum zone_stat_item {
>  	NR_ZONE_INACTIVE_FILE,
>  	NR_ZONE_ACTIVE_FILE,
>  	NR_ZONE_UNEVICTABLE,
> +	NR_ZONE_LAZYFREE,
>  	NR_ZONE_WRITE_PENDING,	/* Count of dirty, writeback and unstable pages */
>  	NR_MLOCK,		/* mlock()ed pages found and moved off LRU */
>  	NR_SLAB_RECLAIMABLE,
> @@ -147,6 +148,7 @@ enum node_stat_item {
>  	NR_INACTIVE_FILE,	/*  "     "     "   "       "         */
>  	NR_ACTIVE_FILE,		/*  "     "     "   "       "         */
>  	NR_UNEVICTABLE,		/*  "     "     "   "       "         */
> +	NR_LAZYFREE,		/*  "     "     "   "       "         */
>  	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 */
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 11b4cd4..d0ff8c2 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4453,7 +4453,7 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
>  		" unevictable:%lu dirty:%lu writeback:%lu unstable:%lu\n"
>  		" slab_reclaimable:%lu slab_unreclaimable:%lu\n"
>  		" mapped:%lu shmem:%lu pagetables:%lu bounce:%lu\n"
> -		" free:%lu free_pcp:%lu free_cma:%lu\n",
> +		" free:%lu free_pcp:%lu free_cma:%lu lazy_free:%lu\n",
>  		global_node_page_state(NR_ACTIVE_ANON),
>  		global_node_page_state(NR_INACTIVE_ANON),
>  		global_node_page_state(NR_ISOLATED_ANON),
> @@ -4472,7 +4472,8 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
>  		global_page_state(NR_BOUNCE),
>  		global_page_state(NR_FREE_PAGES),
>  		free_pcp,
> -		global_page_state(NR_FREE_CMA_PAGES));
> +		global_page_state(NR_FREE_CMA_PAGES),
> +		global_node_page_state(NR_LAZYFREE));
>  
>  	for_each_online_pgdat(pgdat) {
>  		if (show_mem_node_skip(filter, pgdat->node_id, nodemask))
> @@ -4484,6 +4485,7 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
>  			" active_file:%lukB"
>  			" inactive_file:%lukB"
>  			" unevictable:%lukB"
> +			" lazy_free:%lukB"
>  			" isolated(anon):%lukB"
>  			" isolated(file):%lukB"
>  			" mapped:%lukB"
> @@ -4506,6 +4508,7 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
>  			K(node_page_state(pgdat, NR_ACTIVE_FILE)),
>  			K(node_page_state(pgdat, NR_INACTIVE_FILE)),
>  			K(node_page_state(pgdat, NR_UNEVICTABLE)),
> +			K(node_page_state(pgdat, NR_LAZYFREE)),
>  			K(node_page_state(pgdat, NR_ISOLATED_ANON)),
>  			K(node_page_state(pgdat, NR_ISOLATED_FILE)),
>  			K(node_page_state(pgdat, NR_FILE_MAPPED)),
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index b304a84..1a98467 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1442,7 +1442,8 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode)
>   * be complete before mem_cgroup_update_lru_size due to a santity check.
>   */
>  static __always_inline void update_lru_sizes(struct lruvec *lruvec,
> -			enum lru_list lru, unsigned long *nr_zone_taken)
> +			enum lru_list lru, unsigned long *nr_zone_taken,
> +			unsigned long *nr_zone_lazyfree)
>  {
>  	int zid;
>  
> @@ -1450,6 +1451,7 @@ static __always_inline void update_lru_sizes(struct lruvec *lruvec,
>  		if (!nr_zone_taken[zid])
>  			continue;
>  
> +		__update_lazyfree_size(lruvec, zid, -nr_zone_lazyfree[zid]);
>  		__update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
>  #ifdef CONFIG_MEMCG
>  		mem_cgroup_update_lru_size(lruvec, lru, zid, -nr_zone_taken[zid]);
> @@ -1486,6 +1488,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>  	struct list_head *src = &lruvec->lists[lru];
>  	unsigned long nr_taken = 0;
>  	unsigned long nr_zone_taken[MAX_NR_ZONES] = { 0 };
> +	unsigned long nr_zone_lazyfree[MAX_NR_ZONES] = { 0 };
>  	unsigned long nr_skipped[MAX_NR_ZONES] = { 0, };
>  	unsigned long skipped = 0, total_skipped = 0;
>  	unsigned long scan, nr_pages;
> @@ -1517,6 +1520,8 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>  			nr_pages = hpage_nr_pages(page);
>  			nr_taken += nr_pages;
>  			nr_zone_taken[page_zonenum(page)] += nr_pages;
> +			if (page_is_lazyfree(page))
> +				nr_zone_lazyfree[page_zonenum(page)] += nr_pages;
>  			list_move(&page->lru, dst);
>  			break;
>  
> @@ -1560,7 +1565,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>  	*nr_scanned = scan + total_skipped;
>  	trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, nr_to_scan,
>  				    scan, skipped, nr_taken, mode, lru);
> -	update_lru_sizes(lruvec, lru, nr_zone_taken);
> +	update_lru_sizes(lruvec, lru, nr_zone_taken, nr_zone_lazyfree);
>  	return nr_taken;
>  }
>  
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 7774196..a70b52d 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -926,6 +926,7 @@ const char * const vmstat_text[] = {
>  	"nr_zone_inactive_file",
>  	"nr_zone_active_file",
>  	"nr_zone_unevictable",
> +	"nr_zone_lazyfree",
>  	"nr_zone_write_pending",
>  	"nr_mlock",
>  	"nr_slab_reclaimable",
> @@ -952,6 +953,7 @@ const char * const vmstat_text[] = {
>  	"nr_inactive_file",
>  	"nr_active_file",
>  	"nr_unevictable",
> +	"nr_lazyfree",
>  	"nr_isolated_anon",
>  	"nr_isolated_file",
>  	"nr_pages_scanned",
> -- 
> 2.9.3
> 

-- 
Michal Hocko
SUSE Labs