linux-kernel - [PATCH 1/2] zsmalloc: do not remap dst page while prepare next src page

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Date:	Wed, 25 Mar 2015 00:24:46 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>
Cc:	Nitin Gupta <ngupta@...are.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: [PATCH 1/2] zsmalloc: do not remap dst page while prepare next src page

object may belong to different pages. zs_object_copy() handles
this case and maps a new source page (get_next_page() and
kmap_atomic()) when object crosses boundaries of the current
source page. But it also performs unnecessary kunmap/kmap_atomic
of the destination page (it remains unchanged), which can be
avoided.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
---
 mm/zsmalloc.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index d920e8b..7af4456 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1536,12 +1536,10 @@ static void zs_object_copy(unsigned long src, unsigned long dst,
 			break;
 
 		if (s_off + size >= PAGE_SIZE) {
-			kunmap_atomic(d_addr);
 			kunmap_atomic(s_addr);
 			s_page = get_next_page(s_page);
 			BUG_ON(!s_page);
 			s_addr = kmap_atomic(s_page);
-			d_addr = kmap_atomic(d_page);
 			s_size = class->size - written;
 			s_off = 0;
 		} else {
-- 
2.3.4

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