[PATCH v2] cgroup: prefer [kv]zalloc[_node] over [kv]malloc+memset in memory controller code.

Jesper Juhl jj at chaosbits.net
Thu Nov 4 13:17:27 PDT 2010


Hi,

In mem_cgroup_alloc() we currently do either kmalloc() or vmalloc() then 
followed by memset() to zero the memory. This can be more efficiently 
achieved by using kzalloc() and vzalloc().
There's also one situation where we can use kzalloc_node() - this is 
what's new in this version of the patch.

The original patch was:

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu at jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim at gmail.com>
Reviewed-by: Wu Fengguang <fengguang.wu at intel.com>
Acked-by: Balbir Singh <balbir at linux.vnet.ibm.com>

Here's version 2. I'd appreciate it if someone could merge it, but I don't 
know who that someone would be.


Signed-off-by: Jesper Juhl <jj at chaosbits.net>
---
 memcontrol.c |    9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9a99cfa..4f4e676 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4169,13 +4169,11 @@ static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
 	 */
 	if (!node_state(node, N_NORMAL_MEMORY))
 		tmp = -1;
-	pn = kmalloc_node(sizeof(*pn), GFP_KERNEL, tmp);
+	pn = kzalloc_node(sizeof(*pn), GFP_KERNEL, tmp);
 	if (!pn)
 		return 1;
 
 	mem->info.nodeinfo[node] = pn;
-	memset(pn, 0, sizeof(*pn));
-
 	for (zone = 0; zone < MAX_NR_ZONES; zone++) {
 		mz = &pn->zoneinfo[zone];
 		for_each_lru(l)
@@ -4199,14 +4197,13 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
 
 	/* Can be very big if MAX_NUMNODES is very big */
 	if (size < PAGE_SIZE)
-		mem = kmalloc(size, GFP_KERNEL);
+		mem = kzalloc(size, GFP_KERNEL);
 	else
-		mem = vmalloc(size);
+		mem = vzalloc(size);
 
 	if (!mem)
 		return NULL;
 
-	memset(mem, 0, size);
 	mem->stat = alloc_percpu(struct mem_cgroup_stat_cpu);
 	if (!mem->stat) {
 		if (size < PAGE_SIZE)


-- 
Jesper Juhl <jj at chaosbits.net>             http://www.chaosbits.net/
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