Re: [RFC 1/8] Only isolate page we can handle

[Mel Gorman]

On Wed, Apr 27, 2011 at 01:25:18AM +0900, Minchan Kim wrote:
> There are some places to isolate lru page and I believe
> users of isolate_lru_page will be growing.
> The purpose of them is each different so part of isolated pages
> should put back to LRU, again.
> 
> The problem is when we put back the page into LRU,
> we lose LRU ordering and the page is inserted at head of LRU list.
> It makes unnecessary LRU churning so that vm can evict working set pages
> rather than idle pages.
> 
> This patch adds new filter mask when we isolate page in LRU.
> So, we don't isolate pages if we can't handle it.
> It could reduce LRU churning.
> 
> This patch shouldn't change old behavior.
> It's just used by next patches.
> 
> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxx>
> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx>
> ---
>  include/linux/swap.h |    3 ++-
>  mm/compaction.c      |    2 +-
>  mm/memcontrol.c      |    2 +-
>  mm/vmscan.c          |   26 ++++++++++++++++++++------
>  4 files changed, 24 insertions(+), 9 deletions(-)
> 
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 384eb5f..baef4ad 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -259,7 +259,8 @@ extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
>  						unsigned int swappiness,
>  						struct zone *zone,
>  						unsigned long *nr_scanned);
> -extern int __isolate_lru_page(struct page *page, int mode, int file);
> +extern int __isolate_lru_page(struct page *page, int mode, int file,
> +				int not_dirty, int not_mapped);

bool? If you use bitmask later, it's not important though.

>  extern unsigned long shrink_all_memory(unsigned long nr_pages);
>  extern int vm_swappiness;
>  extern int remove_mapping(struct address_space *mapping, struct page *page);
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 021a296..dea32e3 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -335,7 +335,7 @@ static unsigned long isolate_migratepages(struct zone *zone,
>  		}
>  
>  		/* Try isolate the page */
> -		if (__isolate_lru_page(page, ISOLATE_BOTH, 0) != 0)
> +		if (__isolate_lru_page(page, ISOLATE_BOTH, 0, 0, 0) != 0)
>  			continue;
>  
>  		VM_BUG_ON(PageTransCompound(page));
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index c2776f1..471e7fd 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1193,7 +1193,7 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
>  			continue;
>  
>  		scan++;
> -		ret = __isolate_lru_page(page, mode, file);
> +		ret = __isolate_lru_page(page, mode, file, 0, 0);
>  		switch (ret) {
>  		case 0:
>  			list_move(&page->lru, dst);
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index b3a569f..71d2da9 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -954,10 +954,13 @@ keep_lumpy:
>   *
>   * page:	page to consider
>   * mode:	one of the LRU isolation modes defined above
> - *
> + * file:	page be on a file LRU
> + * not_dirty:	page should be not dirty or not writeback
> + * not_mapped:	page should be not mapped
>   * returns 0 on success, -ve errno on failure.
>   */
> -int __isolate_lru_page(struct page *page, int mode, int file)
> +int __isolate_lru_page(struct page *page, int mode, int file,
> +				int not_dirty, int not_mapped)
>  {
>  	int ret = -EINVAL;
>  
> @@ -976,6 +979,12 @@ int __isolate_lru_page(struct page *page, int mode, int file)
>  	if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
>  		return ret;
>  
> +	if (not_dirty)
> +		if (PageDirty(page) || PageWriteback(page))
> +			return ret;
> +	if (not_mapped)
> +		if (page_mapped(page))
> +			return ret;
>  	/*
>  	 * When this function is being called for lumpy reclaim, we
>  	 * initially look into all LRU pages, active, inactive and
> @@ -1016,12 +1025,15 @@ int __isolate_lru_page(struct page *page, int mode, int file)
>   * @order:	The caller's attempted allocation order
>   * @mode:	One of the LRU isolation modes
>   * @file:	True [1] if isolating file [!anon] pages
> + * @not_dirty:	True [1] if isolating file [!dirty] pages
> + * @not_mapped:	True [1] if isolating file [!mapped] pages
>   *
>   * returns how many pages were moved onto *@dst.
>   */
>  static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>  		struct list_head *src, struct list_head *dst,
> -		unsigned long *scanned, int order, int mode, int file)
> +		unsigned long *scanned, int order, int mode, int file,
> +		int not_dirty, int not_mapped)
>  {
>  	unsigned long nr_taken = 0;
>  	unsigned long nr_lumpy_taken = 0;
> @@ -1041,7 +1053,8 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>  
>  		VM_BUG_ON(!PageLRU(page));
>  
> -		switch (__isolate_lru_page(page, mode, file)) {
> +		switch (__isolate_lru_page(page, mode, file,
> +					not_dirty, not_mapped)) {
>  		case 0:
>  			list_move(&page->lru, dst);
>  			mem_cgroup_del_lru(page);
> @@ -1100,7 +1113,8 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>  			    !PageSwapCache(cursor_page))
>  				break;
>  
> -			if (__isolate_lru_page(cursor_page, mode, file) == 0) {
> +			if (__isolate_lru_page(cursor_page, mode, file,
> +					not_dirty, not_mapped) == 0) {
>  				list_move(&cursor_page->lru, dst);
>  				mem_cgroup_del_lru(cursor_page);
>  				nr_taken += hpage_nr_pages(page);
> @@ -1143,7 +1157,7 @@ static unsigned long isolate_pages_global(unsigned long nr,
>  	if (file)
>  		lru += LRU_FILE;
>  	return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order,
> -								mode, file);
> +					mode, file, 0, 0);
>  }
>  
>  /*
> -- 
> 1.7.1
> 

-- 
Mel Gorman
SUSE Labs
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