From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 9 Sep 2008 14:12:44 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [RFC][PATCH] Remove cgroup member from struct page Message-Id: <20080909141244.721dfd39.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <200809091500.10619.nickpiggin@yahoo.com.au> References: <20080901161927.a1fe5afc.kamezawa.hiroyu@jp.fujitsu.com> <200809091358.28350.nickpiggin@yahoo.com.au> <20080909135317.cbff4871.kamezawa.hiroyu@jp.fujitsu.com> <200809091500.10619.nickpiggin@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: balbir@linux.vnet.ibm.com, Andrew Morton , hugh@veritas.com, menage@google.com, xemul@openvz.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Tue, 9 Sep 2008 15:00:10 +1000 Nick Piggin wrote: > > maybe a routine like SPARSEMEM is a choice. > > > > Following is pointer pre-allocation. (just pointer, not page_cgroup itself) > > == > > #define PCG_SECTION_SHIFT (10) > > #define PCG_SECTION_SIZE (1 << PCG_SECTION_SHIFT) > > > > struct pcg_section { > > struct page_cgroup **map[PCG_SECTION_SHIFT]; //array of pointer. > > }; > > > > struct page_cgroup *get_page_cgroup(unsigned long pfn) > > { > > struct pcg_section *sec; > > sec = pcg_section[(pfn >> PCG_SECTION_SHIFT)]; > > return *sec->page_cgroup[(pfn & ((1 << PCG_SECTTION_SHIFT) - 1]; > > } > > == > > If we go extreme, we can use kmap_atomic() for pointer array. > > > > Overhead of pointer-walk is not so bad, maybe. > > > > For 64bit systems, we can find a way like SPARSEMEM_VMEMMAP. > > Yes I too think that would be the ideal way to go to get the best of > performance in the enabled case. However Balbir I believe is interested > in memory savings if not all pages have cgroups... I don't know, I don't > care so much about the "enabled" case, so I'll leave you two to fight it > out :) > I'll add a new patch on my set. Balbir, are you ok to CONFIG_CGROUP_MEM_RES_CTLR depends on CONFIG_SPARSEMEM ? I thinks SPARSEMEM(SPARSEMEM_VMEMMAP) is widely used in various archs now. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org