Messages in this thread | | | Date | Fri, 12 Sep 2008 09:12:48 -0700 | From | Balbir Singh <> | Subject | Re: [RFC] [PATCH 8/9] memcg: remove page_cgroup pointer from memmap |
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KAMEZAWA Hiroyuki wrote: > Remove page_cgroup pointer from struct page. > > This patch removes page_cgroup pointer from struct page and make it be able > to get from pfn. Then, relationship of them is > > Before this: > pfn <-> struct page <-> struct page_cgroup. > After this: > struct page <-> pfn -> struct page_cgroup -> struct page. > > Benefit of this approach is we can remove 8(4) bytes from struct page. > > Other changes are: > - lock/unlock_page_cgroup() uses its own bit on struct page_cgroup. > - all necessary page_cgroups are allocated at boot. > > Characteristics: > - page cgroup is allocated as some amount of chunk. > This patch uses SECTION_SIZE as size of chunk if 64bit/SPARSEMEM is enabled. > If not, appropriate default number is selected. > - all page_cgroup struct is maintained by hash. > I think we have 2 ways to handle sparse index in general > ...radix-tree and hash. This uses hash because radix-tree's layout is > affected by memory map's layout. > - page_cgroup.h/page_cgroup.c is added. > > TODO: > - memory hotplug support. (not difficult)
Kamezawa,
I feel we can try the following approaches
1. Try per-node per-zone radix tree with dynamic allocation 2. Try the approach you have 3. Integrate with sparsemem (last resort for performance), Dave Hansen suggested adding a mem_section member and using that.
I am going to try #1 today and see what the performance looks like
-- Balbir
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