Messages in this thread Patch in this message | | | Date | Wed, 2 Jul 2008 11:16:18 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [RFC][PATCH] memcg: shmem swap cache |
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On Tue, 1 Jul 2008 09:56:45 +0900 (JST) kamezawa.hiroyu@jp.fujitsu.com wrote:
> >> - shmem's page is removed by mem_cgroup_uncharge_cache_page(), So, > >> shmem's swapcache is not charged. > > > >Ah, that's interesting: I'd assumed you'd changed that in your > >no-refcount patches, and had been surprised not to notice a slowdown > >(waiting for swap to be written and freed before coming under limit). > >Now you want to make them wait: not entirely an improvement, > >but I see your point. > > > To do this is (maybe) a few line patch. I'll CC you if I wrote some. > maybe like this. how do you feel ? I'll stack this on my queue and test for a while.
== SwapCache handling fix.
memcg failed to handle shmem's swapcache. This patch tries to fix it.
After this:
Any page marked as SwapCache is not uncharged. (until delelte_from_swap_cache() delete the flag.)
To check a page is alive shmem-page-cache or not we use page->mapping && !PageAnon(page) instead of pc->flags & PAGE_CGROUP_FLAG_CACHE.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Index: test-2.6.26-rc5-mm3++/mm/memcontrol.c =================================================================== --- test-2.6.26-rc5-mm3++.orig/mm/memcontrol.c 2008-07-02 09:29:52.000000000 +0900 +++ test-2.6.26-rc5-mm3++/mm/memcontrol.c 2008-07-02 10:58:15.000000000 +0900 @@ -685,11 +685,45 @@ VM_BUG_ON(pc->page != page); - if ((ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED) - && ((pc->flags & PAGE_CGROUP_FLAG_CACHE) - || page_mapped(page) - || PageSwapCache(page))) + /* + * File Cache + * If called with MEM_CGROUP_CHARGE_TYPE_MAPPED, check page->mapping. + * add_to_page_cache() .... charged before inserting radix-tree. + * remove_from_page_cache() .... uncharged at removing from radix-tree. + * page->mapping && !PageAnon(page) catches file cache. + * + * Anon/Shmem.....We check PageSwapCache(page). + * Anon .... charged before mapped. + * Shmem .... charged at add_to_page_cache() as usual File Cache. + * + * This page will be finally uncharged when removed from swap-cache + * + * we treat 2 cases here. + * A. anonymous page B. shmem. + * We never uncharge if page is marked as SwapCache. + * add_to_swap_cache() have nothing to do with charge/uncharge. + * SwapCache flag is deleted before delete_from_swap_cache() calls this + * + * shmem's behavior is following. (see shmem.c/swap_state.c also) + * at swap-out: + * 0. add_to_page_cache()//charged at page creation. + * 1. add_to_swap_cache() (marked as SwapCache) + * 2. remove_from_page_cache(). (calls this.) + * (finally) delete_from_swap_cache(). (calls this.) + * at swap-in: + * 3. add_to_swap_cache() (no charge here.) + * 4. add_to_page_cache() (charged here.) + * 5. delete_from_swap_cache() (calls this.) + * PageSwapCache(page) catches "2". + * page->mapping && !PageAnon() catches "5" and avoid uncharging. + */ + if (PageSwapCache(page)) goto unlock; + /* called from unmap or delete_from_swap_cache() */ + if ((ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED) + && (page_mapped(page) + || (page->mapping && !PageAnon(page))))/* alive cache ? */ + goto unlock; mz = page_cgroup_zoneinfo(pc); spin_lock_irqsave(&mz->lru_lock, flags);
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