linux-kernel - Re: [PATCH 0/2] zsmalloc: small compaction improvements

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Date:   Fri, 23 Jun 2023 10:03:23 -0700
From:   Minchan Kim <minchan@...nel.org>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] zsmalloc: small compaction improvements

On Fri, Jun 23, 2023 at 01:40:00PM +0900, Sergey Senozhatsky wrote:
> Hi,
> 	A tiny series that can reduce the number of
> find_alloced_obj() invocations (which perform a linear
> scan of sub-page) during compaction. Inspired by Alexey
> Romanov's findings.
> 

Both patches looks good to me.

In this chance, can we have little more cleanup after these two patches?

>From 3cfd4bb0bf395e271f270ee16cb08964ff785a3a Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan@...nel.org>
Date: Fri, 23 Jun 2023 09:45:33 -0700
Subject: [PATCH] zsmalloc: remove zs_compact_control

__zs_compact always putback src_zspage into class list after
migrate_zspage. Thus, we don't need to keep last position of
src_zspage any more. Let's remove it.

Signed-off-by: Minchan Kim <minchan@...nel.org>
---
 mm/zsmalloc.c | 37 +++++++++----------------------------
 1 file changed, 9 insertions(+), 28 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 4a84f7877669..84beadc088b8 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1590,25 +1590,14 @@ static unsigned long find_alloced_obj(struct size_class *class,
 	return find_tagged_obj(class, page, obj_idx, OBJ_ALLOCATED_TAG);
 }
 
-struct zs_compact_control {
-	/* Source spage for migration which could be a subpage of zspage */
-	struct page *s_page;
-	/* Destination page for migration which should be a first page
-	 * of zspage. */
-	struct page *d_page;
-	 /* Starting object index within @s_page which used for live object
-	  * in the subpage. */
-	int obj_idx;
-};
-
-static void migrate_zspage(struct zs_pool *pool, struct size_class *class,
-			   struct zs_compact_control *cc)
+static void migrate_zspage(struct zs_pool *pool, struct zspage *src_zspage,
+			   struct zspage *dst_zspage)
 {
 	unsigned long used_obj, free_obj;
 	unsigned long handle;
-	struct page *s_page = cc->s_page;
-	struct page *d_page = cc->d_page;
-	int obj_idx = cc->obj_idx;
+	int obj_idx = 0;
+	struct page *s_page = get_first_page(src_zspage);
+	struct size_class *class = pool->size_class[src_zspage->class];
 
 	while (1) {
 		handle = find_alloced_obj(class, s_page, &obj_idx);
@@ -1621,24 +1610,20 @@ static void migrate_zspage(struct zs_pool *pool, struct size_class *class,
 		}
 
 		used_obj = handle_to_obj(handle);
-		free_obj = obj_malloc(pool, get_zspage(d_page), handle);
+		free_obj = obj_malloc(pool, dst_zspage, handle);
 		zs_object_copy(class, free_obj, used_obj);
 		obj_idx++;
 		record_obj(handle, free_obj);
 		obj_free(class->size, used_obj);
 
 		/* Stop if there is no more space */
-		if (zspage_full(class, get_zspage(d_page)))
+		if (zspage_full(class, dst_zspage))
 			break;
 
 		/* Stop if there are no more objects to migrate */
-		if (zspage_empty(get_zspage(s_page)))
+		if (zspage_empty(src_zspage))
 			break;
 	}
-
-	/* Remember last position in this iteration */
-	cc->s_page = s_page;
-	cc->obj_idx = obj_idx;
 }
 
 static struct zspage *isolate_src_zspage(struct size_class *class)
@@ -2013,7 +1998,6 @@ static unsigned long zs_can_compact(struct size_class *class)
 static unsigned long __zs_compact(struct zs_pool *pool,
 				  struct size_class *class)
 {
-	struct zs_compact_control cc;
 	struct zspage *src_zspage = NULL;
 	struct zspage *dst_zspage = NULL;
 	unsigned long pages_freed = 0;
@@ -2031,7 +2015,6 @@ static unsigned long __zs_compact(struct zs_pool *pool,
 			if (!dst_zspage)
 				break;
 			migrate_write_lock(dst_zspage);
-			cc.d_page = get_first_page(dst_zspage);
 		}
 
 		src_zspage = isolate_src_zspage(class);
@@ -2040,9 +2023,7 @@ static unsigned long __zs_compact(struct zs_pool *pool,
 
 		migrate_write_lock_nested(src_zspage);
 
-		cc.obj_idx = 0;
-		cc.s_page = get_first_page(src_zspage);
-		migrate_zspage(pool, class, &cc);
+		migrate_zspage(pool, src_zspage, dst_zspage);
 		fg = putback_zspage(class, src_zspage);
 		migrate_write_unlock(src_zspage);
 
-- 
2.41.0.178.g377b9f9a00-goog