linux-kernel - [PATCH v1 2/2] zsmalloc: check empty page in find_alloced

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Message-ID: <20230619143506.45253-3-avromanov@sberdevices.ru>
Date:   Mon, 19 Jun 2023 17:35:06 +0300
From:   Alexey Romanov <avromanov@...rdevices.ru>
To:     <minchan@...nel.org>, <senozhatsky@...omium.org>,
        <akpm@...ux-foundation.org>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <kernel@...rdevices.ru>, Alexey Romanov <avromanov@...rdevices.ru>
Subject: [PATCH v1 2/2] zsmalloc: check empty page in find_alloced_obj

It makes no sense to search for an allocated object
if there are none on the page. Using this check, we
get rid of the extra kmap_atomic, as well as the search
for a tagged object. On my synthetic test data, this
change speed up zsmalloc compaction time by up to 10%.

Signed-off-by: Alexey Romanov <avromanov@...rdevices.ru>
---
 mm/zsmalloc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index dd6e2c3429e0..d0ce579dcde5 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1764,6 +1764,9 @@ static unsigned long find_tagged_obj(struct size_class *class,
 static unsigned long find_alloced_obj(struct size_class *class,
 					struct page *page, int *obj_idx)
 {
+	if (!get_obj_allocated(page))
+		return 0;
+
 	return find_tagged_obj(class, page, obj_idx, OBJ_ALLOCATED_TAG);
 }
 
-- 
2.38.1