Re: [PATCH v1 09/19] zsmalloc: keep max_object in size_class

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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@xxxxxxxxxx>
---
  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;



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