Commit 860c707d authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Linus Torvalds
Browse files

zsmalloc: account the number of compacted pages 



Compaction returns back to zram the number of migrated objects, which is
quite uninformative -- we have objects of different sizes so user space
cannot obtain any valuable data from that number.  Change compaction to
operate in terms of pages and return back to compaction issuer the
number of pages that were freed during compaction.  So from now on we
will export more meaningful value in zram<id>/mm_stat -- the number of
freed (compacted) pages.

This requires:
 (a) a rename of `num_migrated' to 'pages_compacted'
 (b) a internal API change -- return first_page's fullness_group from
     putback_zspage(), so we know when putback_zspage() did
     free_zspage().  It helps us to account compaction stats correctly.

Signed-off-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: default avatarMinchan Kim <minchan@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7d3f3938

Documentation/blockdev/zram.txt

+2 −1
Original line number Diff line number Diff line
@@ -144,7 +144,8 @@ mem_used_max RW the maximum amount memory zram have consumed to 
                        store compressed data

mem_limit         RW    the maximum amount of memory ZRAM can use to store

                        the compressed data

num_migrated      RO    the number of objects migrated migrated by compaction

pages_compacted   RO    the number of pages freed during compaction

                        (available only via zram<id>/mm_stat node)

compact           WO    trigger memory compaction



WARNING

drivers/block/zram/zram_drv.c

+1 −1
Original line number Diff line number Diff line
@@ -450,7 +450,7 @@ static ssize_t mm_stat_show(struct device *dev, 
			zram->limit_pages << PAGE_SHIFT,

			max_used << PAGE_SHIFT,

			(u64)atomic64_read(&zram->stats.zero_pages),

			pool_stats.num_migrated);

			pool_stats.pages_compacted);

	up_read(&zram->init_lock);



	return ret;

include/linux/zsmalloc.h

+2 −2
Original line number Diff line number Diff line
@@ -35,8 +35,8 @@ enum zs_mapmode { 
};



struct zs_pool_stats {

	/* How many objects were migrated */

	unsigned long num_migrated;

	/* How many pages were migrated (freed) */

	unsigned long pages_compacted;

};



struct zs_pool;

mm/zsmalloc.c

+17 −10
Original line number Diff line number Diff line
@@ -1579,8 +1579,6 @@ struct zs_compact_control { 
	 /* Starting object index within @s_page which used for live object

	  * in the subpage. */

	int index;

	/* How many of objects were migrated */

	int nr_migrated;

};



static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
@@ -1617,7 +1615,6 @@ static int migrate_zspage(struct zs_pool *pool, struct size_class *class, 
		record_obj(handle, free_obj);

		unpin_tag(handle);

		obj_free(pool, class, used_obj);

		cc->nr_migrated++;

	}



	/* Remember last position in this iteration */
@@ -1643,7 +1640,16 @@ static struct page *isolate_target_page(struct size_class *class) 
	return page;

}



static void putback_zspage(struct zs_pool *pool, struct size_class *class,

/*

 * putback_zspage - add @first_page into right class's fullness list

 * @pool: target pool

 * @class: destination class

 * @first_page: target page

 *

 * Return @fist_page's fullness_group

 */

static enum fullness_group putback_zspage(struct zs_pool *pool,

			struct size_class *class,

			struct page *first_page)

{

	enum fullness_group fullness;
@@ -1662,6 +1668,8 @@ static void putback_zspage(struct zs_pool *pool, struct size_class *class, 


		free_zspage(first_page);

	}



	return fullness;

}



static struct page *isolate_source_page(struct size_class *class)
@@ -1704,7 +1712,6 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class) 
	struct page *src_page;

	struct page *dst_page = NULL;



	cc.nr_migrated = 0;

	spin_lock(&class->lock);

	while ((src_page = isolate_source_page(class))) {
@@ -1733,7 +1740,9 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class) 
			break;



		putback_zspage(pool, class, dst_page);

		putback_zspage(pool, class, src_page);

		if (putback_zspage(pool, class, src_page) == ZS_EMPTY)

			pool->stats.pages_compacted +=

				get_pages_per_zspage(class->size);

		spin_unlock(&class->lock);

		cond_resched();

		spin_lock(&class->lock);
@@ -1742,8 +1751,6 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class) 
	if (src_page)

		putback_zspage(pool, class, src_page);



	pool->stats.num_migrated += cc.nr_migrated;



	spin_unlock(&class->lock);

}
@@ -1761,7 +1768,7 @@ unsigned long zs_compact(struct zs_pool *pool) 
		__zs_compact(pool, class);

	}



	return pool->stats.num_migrated;

	return pool->stats.pages_compacted;

}

EXPORT_SYMBOL_GPL(zs_compact);

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