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Date: Thu, 22 Jul 2010 14:43:56 +0900 From: Daisuke Nishimura <nishimura@....nes.nec.co.jp> To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> Cc: "linux-mm@...ck.org" <linux-mm@...ck.org>, "balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Daisuke Nishimura <nishimura@....nes.nec.co.jp> Subject: Re: [RFC][PATCH 1/2][memcg] moving memcg's node info array to virtually contiguous array On Wed, 21 Jul 2010 19:58:31 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote: > These are just a _toy_ level patches yet. My final purpose is to use indexed array > for mem_cgroup itself, it has IDs. > > Background: > memory cgroup uses struct page_cgroup for tracking all used pages. It's defined as > == > struct page_cgroup { > unsigned long flags; > struct mem_cgroup *mem_cgroup; > struct page *page; > struct list_head lru; /* per cgroup LRU list */ > }; > == > and this increase the cost of per-page-objects dramatically. Now, we have > troubles on this object. > 1. Recently, a blkio-tracking guy wants to add "blockio-cgroup" information > to page_cgroup. But our concern is extra 8bytes per page. > 2. At tracking dirty page status etc...we need some trick for safe access > to page_cgroup and memcgroup's information. For example, a small seqlock. > > Now, each memory cgroup has its own ID (0-65535). So, if we can replace > 8byte of pointer "pc->mem_cgroup" with an ID, which is 2 bytes, we may able > to have another room. (Moreover, I think we can reduce the number of IDs...) > > This patch is a trial for implement a virually-indexed on-demand array and > an example of usage. Any commetns are welcome. > So, your purpose is to: - make the size of mem_croup small(by [2/2]) - manage all the mem_cgroup in virt-array indexed by its ID(it would be faster than using css_lookup) - replace pc->mem_cgroup by its ID and make the size of page_cgroup small right? Thanks, Daisuke Nishimura. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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