Re: [PATCH v3 1/4] mm: add free_hot_cold_page_list helper

[Hugh Dickins <hughd@google.com>]

On Fri, 11 Nov 2011, Konstantin Khlebnikov wrote:

> This patch adds helper free_hot_cold_page_list() to free list of 0-order pages.
> It frees pages directly from the list without temporary page-vector.
> It also calls trace_mm_pagevec_free() to simulate pagevec_free() behaviour.
> 
> bloat-o-meter:
> 
> add/remove: 1/1 grow/shrink: 1/3 up/down: 267/-295 (-28)
> function                                     old     new   delta
> free_hot_cold_page_list                        -     264    +264
> get_page_from_freelist                      2129    2132      +3
> __pagevec_free                               243     239      -4
> split_free_page                              380     373      -7
> release_pages                                606     510     -96
> free_page_list                               188       -    -188
> 
> v2: Remove list reinititialization.
> v3: Always free pages in reverse order.
>     The most recently added struct page, the most likely to be hot.
> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>

Acked-by: Hugh Dickins <hughd@google.com>

> ---
>  include/linux/gfp.h |    1 +
>  mm/page_alloc.c     |   13 +++++++++++++
>  mm/swap.c           |   14 +++-----------
>  mm/vmscan.c         |   20 +-------------------
>  4 files changed, 18 insertions(+), 30 deletions(-)
> 
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 3a76faf..6562958 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -358,6 +358,7 @@ void *alloc_pages_exact_nid(int nid, size_t size, gfp_t gfp_mask);
>  extern void __free_pages(struct page *page, unsigned int order);
>  extern void free_pages(unsigned long addr, unsigned int order);
>  extern void free_hot_cold_page(struct page *page, int cold);
> +extern void free_hot_cold_page_list(struct list_head *list, int cold);
>  
>  #define __free_page(page) __free_pages((page), 0)
>  #define free_page(addr) free_pages((addr), 0)
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 9dd443d..5093114 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1211,6 +1211,19 @@ out:
>  }
>  
>  /*
> + * Free a list of 0-order pages
> + */
> +void free_hot_cold_page_list(struct list_head *list, int cold)
> +{
> +	struct page *page, *next;
> +
> +	list_for_each_entry_safe(page, next, list, lru) {
> +		trace_mm_pagevec_free(page, cold);
> +		free_hot_cold_page(page, cold);
> +	}
> +}
> +
> +/*
>   * split_page takes a non-compound higher-order page, and splits it into
>   * n (1<<order) sub-pages: page[0..n]
>   * Each sub-page must be freed individually.
> diff --git a/mm/swap.c b/mm/swap.c
> index a91caf7..67a09a6 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -585,11 +585,10 @@ int lru_add_drain_all(void)
>  void release_pages(struct page **pages, int nr, int cold)
>  {
>  	int i;
> -	struct pagevec pages_to_free;
> +	LIST_HEAD(pages_to_free);
>  	struct zone *zone = NULL;
>  	unsigned long uninitialized_var(flags);
>  
> -	pagevec_init(&pages_to_free, cold);
>  	for (i = 0; i < nr; i++) {
>  		struct page *page = pages[i];
>  
> @@ -620,19 +619,12 @@ void release_pages(struct page **pages, int nr, int cold)
>  			del_page_from_lru(zone, page);
>  		}
>  
> -		if (!pagevec_add(&pages_to_free, page)) {
> -			if (zone) {
> -				spin_unlock_irqrestore(&zone->lru_lock, flags);
> -				zone = NULL;
> -			}
> -			__pagevec_free(&pages_to_free);
> -			pagevec_reinit(&pages_to_free);
> -  		}
> +		list_add(&page->lru, &pages_to_free);
>  	}
>  	if (zone)
>  		spin_unlock_irqrestore(&zone->lru_lock, flags);
>  
> -	pagevec_free(&pages_to_free);
> +	free_hot_cold_page_list(&pages_to_free, cold);
>  }
>  EXPORT_SYMBOL(release_pages);
>  
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index a1893c0..f4be53d 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -728,24 +728,6 @@ static enum page_references page_check_references(struct page *page,
>  	return PAGEREF_RECLAIM;
>  }
>  
> -static noinline_for_stack void free_page_list(struct list_head *free_pages)
> -{
> -	struct pagevec freed_pvec;
> -	struct page *page, *tmp;
> -
> -	pagevec_init(&freed_pvec, 1);
> -
> -	list_for_each_entry_safe(page, tmp, free_pages, lru) {
> -		list_del(&page->lru);
> -		if (!pagevec_add(&freed_pvec, page)) {
> -			__pagevec_free(&freed_pvec);
> -			pagevec_reinit(&freed_pvec);
> -		}
> -	}
> -
> -	pagevec_free(&freed_pvec);
> -}
> -
>  /*
>   * shrink_page_list() returns the number of reclaimed pages
>   */
> @@ -1009,7 +991,7 @@ keep_lumpy:
>  	if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc))
>  		zone_set_flag(zone, ZONE_CONGESTED);
>  
> -	free_page_list(&free_pages);
> +	free_hot_cold_page_list(&free_pages, 1);
>  
>  	list_splice(&ret_pages, page_list);
>  	count_vm_events(PGACTIVATE, pgactivate);

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