linux-kernel - Re: [PATCH v1 09/19] zsmalloc: keep max_object in size

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Date:	Sat, 12 Mar 2016 09:44:48 +0800
From:	xuyiping <xuyiping@...ilicon.com>
To:	Minchan Kim <minchan@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
	<jlayton@...chiereds.net>, <bfields@...ldses.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Joonsoo Kim <iamjoonsoo.kim@....com>, <koct9i@...il.com>,
	<aquini@...hat.com>, <virtualization@...ts.linux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	<rknize@...orola.com>, Rik van Riel <riel@...hat.com>,
	Gioh Kim <gurugio@...mail.net>
Subject: Re: [PATCH v1 09/19] zsmalloc: keep max_object in size_class



On 2016/3/11 15:30, Minchan Kim wrote:
> Every zspage in a size_class has same number of max objects so
> we could move it to a size_class.
>
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
>   mm/zsmalloc.c | 29 ++++++++++++++---------------
>   1 file changed, 14 insertions(+), 15 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index b4fb11831acb..ca663c82c1fc 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -32,8 +32,6 @@
>    *	page->freelist: points to the first free object in zspage.
>    *		Free objects are linked together using in-place
>    *		metadata.
> - *	page->objects: maximum number of objects we can store in this
> - *		zspage (class->zspage_order * PAGE_SIZE / class->size)
>    *	page->lru: links together first pages of various zspages.
>    *		Basically forming list of zspages in a fullness group.
>    *	page->mapping: class index and fullness group of the zspage
> @@ -211,6 +209,7 @@ struct size_class {
>   	 * of ZS_ALIGN.
>   	 */
>   	int size;
> +	int objs_per_zspage;
>   	unsigned int index;
>
>   	struct zs_size_stat stats;
> @@ -622,21 +621,22 @@ static inline void zs_pool_stat_destroy(struct zs_pool *pool)
>    * the pool (not yet implemented). This function returns fullness
>    * status of the given page.
>    */
> -static enum fullness_group get_fullness_group(struct page *first_page)
> +static enum fullness_group get_fullness_group(struct size_class *class,
> +						struct page *first_page)
>   {
> -	int inuse, max_objects;
> +	int inuse, objs_per_zspage;
>   	enum fullness_group fg;
>
>   	VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
>
>   	inuse = first_page->inuse;
> -	max_objects = first_page->objects;
> +	objs_per_zspage = class->objs_per_zspage;
>
>   	if (inuse == 0)
>   		fg = ZS_EMPTY;
> -	else if (inuse == max_objects)
> +	else if (inuse == objs_per_zspage)
>   		fg = ZS_FULL;
> -	else if (inuse <= 3 * max_objects / fullness_threshold_frac)
> +	else if (inuse <= 3 * objs_per_zspage / fullness_threshold_frac)
>   		fg = ZS_ALMOST_EMPTY;
>   	else
>   		fg = ZS_ALMOST_FULL;
> @@ -723,7 +723,7 @@ static enum fullness_group fix_fullness_group(struct size_class *class,
>   	enum fullness_group currfg, newfg;
>
>   	get_zspage_mapping(first_page, &class_idx, &currfg);
> -	newfg = get_fullness_group(first_page);
> +	newfg = get_fullness_group(class, first_page);
>   	if (newfg == currfg)
>   		goto out;
>
> @@ -1003,9 +1003,6 @@ static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
>   	init_zspage(class, first_page);
>
>   	first_page->freelist = location_to_obj(first_page, 0);
> -	/* Maximum number of objects we can store in this zspage */
> -	first_page->objects = class->pages_per_zspage * PAGE_SIZE / class->size;
> -
>   	error = 0; /* Success */
>
>   cleanup:
> @@ -1235,11 +1232,11 @@ static bool can_merge(struct size_class *prev, int size, int pages_per_zspage)
>   	return true;
>   }
>
> -static bool zspage_full(struct page *first_page)
> +static bool zspage_full(struct size_class *class, struct page *first_page)
>   {
>   	VM_BUG_ON_PAGE(!is_first_page(first_page), first_page);
>
> -	return first_page->inuse == first_page->objects;
> +	return first_page->inuse == class->objs_per_zspage;
>   }
>
>   unsigned long zs_get_total_pages(struct zs_pool *pool)
> @@ -1625,7 +1622,7 @@ static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
>   		}
>
>   		/* Stop if there is no more space */
> -		if (zspage_full(d_page)) {
> +		if (zspage_full(class, d_page)) {
>   			unpin_tag(handle);
>   			ret = -ENOMEM;
>   			break;
> @@ -1684,7 +1681,7 @@ static enum fullness_group putback_zspage(struct zs_pool *pool,
>   {
>   	enum fullness_group fullness;
>
> -	fullness = get_fullness_group(first_page);
> +	fullness = get_fullness_group(class, first_page);
>   	insert_zspage(class, fullness, first_page);
>   	set_zspage_mapping(first_page, class->index, fullness);
>
> @@ -1933,6 +1930,8 @@ struct zs_pool *zs_create_pool(const char *name, gfp_t flags)
>   		class->size = size;
>   		class->index = i;
>   		class->pages_per_zspage = pages_per_zspage;
> +		class->objs_per_zspage = class->pages_per_zspage *
> +						PAGE_SIZE / class->size;
>   		if (pages_per_zspage == 1 &&
>   			get_maxobj_per_zspage(size, pages_per_zspage) == 1)
>   			class->huge = true;

		computes the "objs_per_zspage" twice here.

		class->objs_per_zspage = get_maxobj_per_zspage(size,
						pages_per_zspage);
		if (pages_per_zspage == 1 && class->objs_per_zspage ==1)
			class->huge = true;

>