linux-kernel - [PATCH] memcg: avoid unnecessary initialization

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Date:	Fri, 9 May 2008 14:59:41 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"xemul@...nvz.org" <xemul@...nvz.org>,
	"yamamoto@...inux.co.jp" <yamamoto@...inux.co.jp>,
	"lizf@...fujitsu.com" <lizf@...fujitsu.com>
Subject: [PATCH] memcg: avoid unnecessary initialization

An easy cut out from memcg: performance improvement patch set.
Tested on: x86-64/linux-2.6.26-rc1-git6

Thanks,
-Kame
==
* remove over-killing initialization (in fast path)
* makeing the condition for PAGE_CGROUP_FLAG_ACTIVE be more obvious.

Signed-off-by: KAMEAZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

---
 mm/memcontrol.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

Index: linux-2.6.26-rc1/mm/memcontrol.c
===================================================================
--- linux-2.6.26-rc1.orig/mm/memcontrol.c
+++ linux-2.6.26-rc1/mm/memcontrol.c
@@ -296,7 +296,7 @@ static void __mem_cgroup_remove_list(str
 		MEM_CGROUP_ZSTAT(mz, MEM_CGROUP_ZSTAT_INACTIVE) -= 1;
 
 	mem_cgroup_charge_statistics(pc->mem_cgroup, pc->flags, false);
-	list_del_init(&pc->lru);
+	list_del(&pc->lru);
 }
 
 static void __mem_cgroup_add_list(struct mem_cgroup_per_zone *mz,
@@ -559,7 +559,7 @@ retry:
 	}
 	unlock_page_cgroup(page);
 
-	pc = kmem_cache_zalloc(page_cgroup_cache, gfp_mask);
+	pc = kmem_cache_alloc(page_cgroup_cache, gfp_mask);
 	if (pc == NULL)
 		goto err;
 
@@ -606,9 +606,14 @@ retry:
 	pc->ref_cnt = 1;
 	pc->mem_cgroup = mem;
 	pc->page = page;
-	pc->flags = PAGE_CGROUP_FLAG_ACTIVE;
+	/*
+	 * If a page is accounted as a page cache, insert to inactive list.
+	 * If anon, insert to active list.
+	 */
 	if (ctype == MEM_CGROUP_CHARGE_TYPE_CACHE)
 		pc->flags = PAGE_CGROUP_FLAG_CACHE;
+	else
+		pc->flags = PAGE_CGROUP_FLAG_ACTIVE;
 
 	lock_page_cgroup(page);
 	if (page_get_page_cgroup(page)) {

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