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authorVladimir Davydov <vdavydov@virtuozzo.com>2016-07-26 15:24:24 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-07-26 16:19:19 -0700
commit4949148ad433f6f11cf837978b2907092ec99f3a (patch)
tree9ae57d8b9d040aaa66c51ce3e62debced020094a /include/linux/page-flags.h
parent452647784b2fccfdeeb976f6f842c6719fb2daac (diff)
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mm: charge/uncharge kmemcg from generic page allocator paths
Currently, to charge a non-slab allocation to kmemcg one has to use alloc_kmem_pages helper with __GFP_ACCOUNT flag. A page allocated with this helper should finally be freed using free_kmem_pages, otherwise it won't be uncharged. This API suits its current users fine, but it turns out to be impossible to use along with page reference counting, i.e. when an allocation is supposed to be freed with put_page, as it is the case with pipe or unix socket buffers. To overcome this limitation, this patch moves charging/uncharging to generic page allocator paths, i.e. to __alloc_pages_nodemask and free_pages_prepare, and zaps alloc/free_kmem_pages helpers. This way, one can use any of the available page allocation functions to get the allocated page charged to kmemcg - it's enough to pass __GFP_ACCOUNT, just like in case of kmalloc and friends. A charged page will be automatically uncharged on free. To make it possible, we need to mark pages charged to kmemcg somehow. To avoid introducing a new page flag, we make use of page->_mapcount for marking such pages. Since pages charged to kmemcg are not supposed to be mapped to userspace, it should work just fine. There are other (ab)users of page->_mapcount - buddy and balloon pages - but we don't conflict with them. In case kmemcg is compiled out or not used at runtime, this patch introduces no overhead to generic page allocator paths. If kmemcg is used, it will be plus one gfp flags check on alloc and plus one page->_mapcount check on free, which shouldn't hurt performance, because the data accessed are hot. Link: http://lkml.kernel.org/r/a9736d856f895bcb465d9f257b54efe32eda6f99.1464079538.git.vdavydov@virtuozzo.com Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@kernel.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/page-flags.h')
-rw-r--r--include/linux/page-flags.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 96084ee74ee8..7c8e82ac2eb7 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -641,6 +641,13 @@ PAGE_MAPCOUNT_OPS(Buddy, BUDDY)
#define PAGE_BALLOON_MAPCOUNT_VALUE (-256)
PAGE_MAPCOUNT_OPS(Balloon, BALLOON)
+/*
+ * If kmemcg is enabled, the buddy allocator will set PageKmemcg() on
+ * pages allocated with __GFP_ACCOUNT. It gets cleared on page free.
+ */
+#define PAGE_KMEMCG_MAPCOUNT_VALUE (-512)
+PAGE_MAPCOUNT_OPS(Kmemcg, KMEMCG)
+
extern bool is_free_buddy_page(struct page *page);
__PAGEFLAG(Isolated, isolated, PF_ANY);