linux-kernel - Re: [PATCH] use vmalloc for mem

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Message-ID: <48040E19.2090007@cn.fujitsu.com>
Date:	Tue, 15 Apr 2008 10:08:25 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"xemul@...nvz.org" <xemul@...nvz.org>, menage@...gle.com,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] use vmalloc for mem_cgroup allocation. v2

KAMEZAWA Hiroyuki wrote:
> On ia64, this kmalloc() requires order-4 pages. But this is not
> necessary to be phisically contiguous. (and x86-32, which has
> small vmalloc area, has small mem_cgroup struct.)
> 
> For here, vmalloc is better.
> 
> Changelog: v1->v2
>  - added memset().
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
> Index: mm-2.6.25-rc8-mm2/mm/memcontrol.c
> ===================================================================
> --- mm-2.6.25-rc8-mm2.orig/mm/memcontrol.c
> +++ mm-2.6.25-rc8-mm2/mm/memcontrol.c
> @@ -31,6 +31,7 @@
>  #include <linux/spinlock.h>
>  #include <linux/fs.h>
>  #include <linux/seq_file.h>
> +#include <linux/vmalloc.h>
>  
>  #include <asm/uaccess.h>
>  
> @@ -992,8 +993,10 @@ mem_cgroup_create(struct cgroup_subsys *
>  	if (unlikely((cont->parent) == NULL)) {
>  		mem = &init_mem_cgroup;
>  		page_cgroup_cache = KMEM_CACHE(page_cgroup, SLAB_PANIC);
> -	} else
> -		mem = kzalloc(sizeof(struct mem_cgroup), GFP_KERNEL);
> +	} else {
> +		mem = vmalloc(sizeof(struct mem_cgroup));
> +		memset(mem, 0, sizeof(*mem));

what if mem == NULL. ;)

> +	}
>  
>  	if (mem == NULL)
>  		return ERR_PTR(-ENOMEM);

So we can move this NULL check to the above else branch, in the if brach,
mem won't be NULL.

> @@ -1011,7 +1014,7 @@ free_out:
>  	for_each_node_state(node, N_POSSIBLE)
>  		free_mem_cgroup_per_zone_info(mem, node);
>  	if (cont->parent != NULL)
> -		kfree(mem);
> +		vfree(mem);
>  	return ERR_PTR(-ENOMEM);
>  }
>  
> @@ -1031,7 +1034,7 @@ static void mem_cgroup_destroy(struct cg
>  	for_each_node_state(node, N_POSSIBLE)
>  		free_mem_cgroup_per_zone_info(mem, node);
>  
> -	kfree(mem_cgroup_from_cont(cont));
> +	vfree(mem_cgroup_from_cont(cont));
>  }
>  
>  static int mem_cgroup_populate(struct cgroup_subsys *ss,
> 
> 
> 
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