linux-kernel - Re: [RFC][PATCHv4 6/7] zsmalloc: account the number of compacted pages

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Message-ID: <20150702021354.GA637@swordfish>
Date:	Thu, 2 Jul 2015 11:13:54 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [RFC][PATCHv4 6/7] zsmalloc: account the number of compacted
 pages

On (07/01/15 16:29), Sergey Senozhatsky wrote:
> 	if (putback_zspage(.. src_page))
> 		pool->num_migrated++;

      pool->num_migrated += class->pages_per_zspage;
Of course.

> (c) or we can check src_page fullness (or simply if src_page->inuse == 0)
> in __zs_compact() and increment ->num_migrated for ZS_EMPTY page. But this
> is what free_zspage() already does.

In other words, something like this (and we don't need nr_migrated in
zs_compact_control anymore). Not a real patch, just to demonstrate the
idea.

---

@@ -1596,8 +1596,6 @@ 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,
@@ -1634,7 +1632,6 @@ 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 */
@@ -1720,7 +1717,6 @@ 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))) {
 
@@ -1748,6 +1744,9 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class)
 		if (dst_page == NULL)
 			break;
 
+		if (!src_page->inuse)
+			pool->num_migrated += class->pages_per_zspage;
+
 		putback_zspage(pool, class, dst_page);
 		putback_zspage(pool, class, src_page);
 		spin_unlock(&class->lock);
@@ -1758,8 +1757,6 @@ static void __zs_compact(struct zs_pool *pool, struct size_class *class)
 	if (src_page)
 		putback_zspage(pool, class, src_page);
 
-	pool->num_migrated += cc.nr_migrated;
-
 	spin_unlock(&class->lock);
 }
 
--
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