linux-kernel - Re: [PATCH 2/6] memcg: allocate page

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Date:	Mon, 6 Oct 2008 15:41:41 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>
Subject: Re: [PATCH 2/6] memcg: allocate page_cgroup at boot

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2008-10-01 16:56:03]:

> Allocate all page_cgroup at boot and remove page_cgroup poitner
> from struct page. This patch adds an interface as
> 
>  struct page_cgroup *lookup_page_cgroup(struct page*)
> 
> All FLATMEM/DISCONTIGMEM/SPARSEMEM  and MEMORY_HOTPLUG is supported.
> 
> Remove page_cgroup pointer reduces the amount of memory by
>  - 4 bytes per PAGE_SIZE.
>  - 8 bytes per PAGE_SIZE
> if memory controller is disabled. (even if configured.)
> 
> On usual 8GB x86-32 server, this saves 8MB of NORMAL_ZONE memory.
> On my x86-64 server with 48GB of memory, this saves 96MB of memory.
> I think this reduction makes sense.
> 
> By pre-allocation, kmalloc/kfree in charge/uncharge are removed. 
> This means
>   - we're not necessary to be afraid of kmalloc faiulre.
>     (this can happen because of gfp_mask type.)
>   - we can avoid calling kmalloc/kfree.
>   - we can avoid allocating tons of small objects which can be fragmented.
>   - we can know what amount of memory will be used for this extra-lru handling.
> 
> I added printk message as
> 
> 	"allocated %ld bytes of page_cgroup"
>         "please try cgroup_disable=memory option if you don't want"
> 
> maybe enough informative for users.
> 
> Changelog: v5 -> v6.
>  * reflected comments.
>  * coding style fixes.
>  * removed "ctype" from uncharge.
>  * improved comment to show FLAT_NODE_MEM_MAP == !SPARSEMEM
>  * fixed errors in !SPARSEMEM codes
>  * removed unused function in !SPARSEMEM codes.
> (start from v5 because of series..)
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

I like this patch very much

Reviewed-by: Balbir Singh <balbir@...ux.vnet.ibm.com>

-- 
	Balbir
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