Re: [RFC 2/8] Basic allocation for higher order page cache pages

[mel@skynet.ie (Mel Gorman)]

On (19/04/07 09:35), Christoph Lameter didst pronounce:
> Variable Order Page Cache: Add basic allocation functions
> 
> Extend __page_cache_alloc to take an order parameter and
> modify caller sites. Modify mapping_set_gfp_mask to set
> __GFP_COMP if the mapping requires higher order allocations.
> 
> put_page() is already capable of handling compound pages. So
> there are no changes needed to release higher order page
> cache pages.
> 
> Signed-off-by: Christoph Lameter <clameter@sgi.com>
> 
> ---
>  include/linux/pagemap.h |   15 +++++++++------
>  mm/filemap.c            |    9 +++++----
>  2 files changed, 14 insertions(+), 10 deletions(-)
> 
> Index: linux-2.6.21-rc7/include/linux/pagemap.h
> ===================================================================
> --- linux-2.6.21-rc7.orig/include/linux/pagemap.h	2007-04-18 21:21:56.000000000 -0700
> +++ linux-2.6.21-rc7/include/linux/pagemap.h	2007-04-18 21:29:02.000000000 -0700
> @@ -32,6 +32,8 @@ static inline void mapping_set_gfp_mask(
>  {
>  	m->flags = (m->flags & ~(__force unsigned long)__GFP_BITS_MASK) |
>  				(__force unsigned long)mask;
> +	if (m->order)
> +		m->flags |= __GFP_COMP;

This might need a comment. It might not be superclear that compound
pages have destructors that know how to lookup the order on free.

>  }
>  
>  /*
> @@ -40,7 +42,7 @@ static inline void mapping_set_gfp_mask(
>   * throughput (it can then be mapped into user
>   * space in smaller chunks for same flexibility).
>   *
> - * Or rather, it _will_ be done in larger chunks.
> + * This is the base page size
>   */
>  #define PAGE_CACHE_SHIFT	PAGE_SHIFT
>  #define PAGE_CACHE_SIZE		PAGE_SIZE
> @@ -52,22 +54,23 @@ static inline void mapping_set_gfp_mask(
>  void release_pages(struct page **pages, int nr, int cold);
>  
>  #ifdef CONFIG_NUMA
> -extern struct page *__page_cache_alloc(gfp_t gfp);
> +extern struct page *__page_cache_alloc(gfp_t gfp, int order);
>  #else
> -static inline struct page *__page_cache_alloc(gfp_t gfp)
> +static inline struct page *__page_cache_alloc(gfp_t gfp, int order)
>  {
> -	return alloc_pages(gfp, 0);
> +	return alloc_pages(gfp, order);
>  }
>  #endif
>  
>  static inline struct page *page_cache_alloc(struct address_space *x)
>  {
> -	return __page_cache_alloc(mapping_gfp_mask(x));
> +	return __page_cache_alloc(mapping_gfp_mask(x), x->order);
>  }
>  
>  static inline struct page *page_cache_alloc_cold(struct address_space *x)
>  {
> -	return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD);
> +	return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD,
> +		x->order);
>  }
>  
>  typedef int filler_t(void *, struct page *);
> Index: linux-2.6.21-rc7/mm/filemap.c
> ===================================================================
> --- linux-2.6.21-rc7.orig/mm/filemap.c	2007-04-18 21:21:56.000000000 -0700
> +++ linux-2.6.21-rc7/mm/filemap.c	2007-04-18 21:28:30.000000000 -0700
> @@ -467,13 +467,13 @@ int add_to_page_cache_lru(struct page *p
>  }
>  
>  #ifdef CONFIG_NUMA
> -struct page *__page_cache_alloc(gfp_t gfp)
> +struct page *__page_cache_alloc(gfp_t gfp, int order)
>  {
>  	if (cpuset_do_page_mem_spread()) {
>  		int n = cpuset_mem_spread_node();
> -		return alloc_pages_node(n, gfp, 0);
> +		return alloc_pages_node(n, gfp, order);
>  	}
> -	return alloc_pages(gfp, 0);
> +	return alloc_pages(gfp, order);
>  }
>  EXPORT_SYMBOL(__page_cache_alloc);
>  #endif
> @@ -803,7 +803,8 @@ grab_cache_page_nowait(struct address_sp
>  		page_cache_release(page);
>  		return NULL;
>  	}
> -	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
> +	page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS,
> +		mapping->order);
>  	if (page && add_to_page_cache_lru(page, mapping, index, GFP_KERNEL)) {
>  		page_cache_release(page);
>  		page = NULL;
> -

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab