The commit is pushed to "branch-rh7-3.10.0-327.18.2.vz7.14.x-ovz" and will
appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.18.2.vz7.14.9
------>
commit 1265d34743919f73ae85326474b67cc192b58b1b
Author: Vladimir Davydov <vdavy...@virtuozzo.com>
Date: Tue May 31 13:14:09 2016 +0400
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.
Signed-off-by: Vladimir Davydov <vdavy...@virtuozzo.com>
---
include/linux/memcontrol.h | 3 ++-
include/linux/page-flags.h | 19 +++++++++++++++++++
mm/memcontrol.c | 4 ++++
mm/page_alloc.c | 4 ++++
4 files changed, 29 insertions(+), 1 deletion(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index d26adf1..48bf2ca 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -23,6 +23,7 @@
#include <linux/vm_event_item.h>
#include <linux/hardirq.h>
#include <linux/jump_label.h>
+#include <linux/page-flags.h>
struct mem_cgroup;
struct page_cgroup;
@@ -617,7 +618,7 @@ memcg_kmem_newpage_charge(struct page *page, gfp_t gfp, int
order)
static inline void
memcg_kmem_uncharge_pages(struct page *page, int order)
{
- if (memcg_kmem_enabled())
+ if (memcg_kmem_enabled() && PageKmemcg(page))
__memcg_kmem_uncharge_pages(page, order);
}
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index cdf83ec..d15d20d 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -523,6 +523,25 @@ static inline void __ClearPageBalloon(struct page *page)
atomic_set(&page->_mapcount, -1);
}
+#define PAGE_KMEMCG_MAPCOUNT_VALUE (-256)
+
+static inline int PageKmemcg(struct page *page)
+{
+ return atomic_read(&page->_mapcount) == PAGE_KMEMCG_MAPCOUNT_VALUE;
+}
+
+static inline void __SetPageKmemcg(struct page *page)
+{
+ VM_BUG_ON_PAGE(atomic_read(&page->_mapcount) != -1, page);
+ atomic_set(&page->_mapcount, PAGE_KMEMCG_MAPCOUNT_VALUE);
+}
+
+static inline void __ClearPageKmemcg(struct page *page)
+{
+ VM_BUG_ON_PAGE(!PageKmemcg(page), page);
+ atomic_set(&page->_mapcount, -1);
+}
+
/*
* If network-based swap is enabled, sl*b must keep track of whether pages
* were allocated from pfmemalloc reserves.
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 8eb4807..1c3fbb2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3555,6 +3555,8 @@ __memcg_kmem_newpage_charge(struct page *page, gfp_t gfp,
int order)
SetPageCgroupUsed(pc);
unlock_page_cgroup(pc);
+ __SetPageKmemcg(page);
+
return true;
}
@@ -3588,6 +3590,8 @@ void __memcg_kmem_uncharge_pages(struct page *page, int
order)
VM_BUG_ON_PAGE(mem_cgroup_is_root(memcg), page);
memcg_uncharge_kmem(memcg, PAGE_SIZE << order);
+
+ __ClearPageKmemcg(page);
}
struct mem_cgroup *__mem_cgroup_from_kmem(void *ptr)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9f02d80..2b04f36 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -748,6 +748,7 @@ static bool free_pages_prepare(struct page *page, unsigned
int order)
if (PageAnon(page))
page->mapping = NULL;
+ memcg_kmem_uncharge_pages(page, order);
for (i = 0; i < (1 << order); i++) {
bad += free_pages_check(page + i);
if (static_key_false(&zero_free_pages))
@@ -2804,6 +2805,9 @@ out:
if (unlikely(!put_mems_allowed(cpuset_mems_cookie) && !page))
goto retry_cpuset;
+ if (page && !memcg_kmem_newpage_charge(page, gfp_mask, order))
+ __free_pages(page, order);
+
return page;
}
EXPORT_SYMBOL(__alloc_pages_nodemask);
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