Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Sergey Senozhatsky <senozhatsky@chromium.org>
To:     Andrew Morton <akpm@linux-foundation.org>,
        Minchan Kim <minchan@kernel.org>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Sergey Senozhatsky <senozhatsky@chromium.org>,
        Alexey Romanov <AVRomanov@sberdevices.ru>
Subject: [PATCHv2 1/3] zsmalloc: do not scan for allocated objects in empty zspage
Date:   Sat, 24 Jun 2023 14:12:14 +0900
Message-ID: <20230624053120.643409-2-senozhatsky@chromium.org>
In-Reply-To: <20230624053120.643409-1-senozhatsky@chromium.org>
References: <20230624053120.643409-1-senozhatsky@chromium.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

zspage migration can terminate as soon as it moves the last
allocated object from the source zspage.  Add a simple helper
zspage_empty() that tests zspage ->inuse on each migration
iteration.

Suggested-by: Alexey Romanov <AVRomanov@sberdevices.ru>
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 mm/zsmalloc.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 3f057970504e..5d60eaedc3b7 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1147,6 +1147,11 @@ static bool zspage_full(struct size_class *class, struct zspage *zspage)
 	return get_zspage_inuse(zspage) == class->objs_per_zspage;
 }
 
+static bool zspage_empty(struct zspage *zspage)
+{
+	return get_zspage_inuse(zspage) == 0;
+}
+
 /**
  * zs_lookup_class_index() - Returns index of the zsmalloc &size_class
  * that hold objects of the provided size.
@@ -1625,6 +1630,10 @@ static void migrate_zspage(struct zs_pool *pool, struct size_class *class,
 		obj_idx++;
 		record_obj(handle, free_obj);
 		obj_free(class->size, used_obj);
+
+		/* Stop if there are no more objects to migrate */
+		if (zspage_empty(get_zspage(s_page)))
+			break;
 	}
 
 	/* Remember last position in this iteration */
-- 
2.41.0.162.gfafddb0af9-goog