When a process tries to allocate a page with the __GFP_KMEMCG flag, the
page allocator will call the corresponding memcg functions to validate
the allocation. Tasks in the root memcg can always proceed.
To avoid adding markers to the page - and a kmem flag that would
necessarily follow, as much as doing page_cgroup lookups for no reason,
whoever is marking its allocations with __GFP_KMEMCG flag is responsible
for telling the page allocator that this is such an allocation at
free_pages() time. This is done by the invocation of
__free_accounted_pages() and free_accounted_pages().
Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
CC: Christoph Lameter <cl@xxxxxxxxx>
CC: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
CC: Michal Hocko <mhocko@xxxxxxx>
CC: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
CC: Johannes Weiner <hannes@xxxxxxxxxxx>
CC: Suleiman Souhlal <suleiman@xxxxxxxxxx>
---
include/linux/gfp.h | 3 +++
mm/page_alloc.c | 38 ++++++++++++++++++++++++++++++++++++++
2 files changed, 41 insertions(+)
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index d8eae4d..029570f 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -370,6 +370,9 @@ extern void free_pages(unsigned long addr, unsigned int order);
extern void free_hot_cold_page(struct page *page, int cold);
extern void free_hot_cold_page_list(struct list_head *list, int cold);
+extern void __free_accounted_pages(struct page *page, unsigned int order);
+extern void free_accounted_pages(unsigned long addr, unsigned int order);
+
#define __free_page(page) __free_pages((page), 0)
#define free_page(addr) free_pages((addr), 0)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b956cec..da341dc 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2532,6 +2532,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
struct page *page = NULL;
int migratetype = allocflags_to_migratetype(gfp_mask);
unsigned int cpuset_mems_cookie;
+ void *handle = NULL;
gfp_mask &= gfp_allowed_mask;
@@ -2543,6 +2544,13 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
return NULL;
/*
+ * Will only have any effect when __GFP_KMEMCG is set.
+ * This is verified in the (always inline) callee
+ */
+ if (!memcg_kmem_new_page(gfp_mask, &handle, order))
+ return NULL;
+
+ /*
* Check the zones suitable for the gfp_mask contain at least one
* valid zone. It's possible to have an empty zonelist as a result
* of GFP_THISNODE and a memoryless node
@@ -2583,6 +2591,8 @@ out:
if (unlikely(!put_mems_allowed(cpuset_mems_cookie) && !page))
goto retry_cpuset;
+ memcg_kmem_commit_page(page, handle, order);
+
return page;
}
EXPORT_SYMBOL(__alloc_pages_nodemask);
@@ -2635,6 +2645,34 @@ void free_pages(unsigned long addr, unsigned int order)
EXPORT_SYMBOL(free_pages);
+/*
+ * __free_accounted_pages and free_accounted_pages will free pages allocated
+ * with __GFP_KMEMCG.
+ *
+ * Those pages are accounted to a particular memcg, embedded in the
+ * corresponding page_cgroup. To avoid adding a hit in the allocator to search
+ * for that information only to find out that it is NULL for users who have no
+ * interest in that whatsoever, we provide these functions.
+ *
+ * The caller knows better which flags it relies on.
+ */
+void __free_accounted_pages(struct page *page, unsigned int order)
+{
+ memcg_kmem_free_page(page, order);
+ __free_pages(page, order);
+}
+EXPORT_SYMBOL(__free_accounted_pages);
+
+void free_accounted_pages(unsigned long addr, unsigned int order)
+{
+ if (addr != 0) {
+ VM_BUG_ON(!virt_addr_valid((void *)addr));
+ memcg_kmem_free_page(virt_to_page((void *)addr), order);
+ __free_pages(virt_to_page((void *)addr), order);
+ }
+}
+EXPORT_SYMBOL(free_accounted_pages);
+
static void *make_alloc_exact(unsigned long addr, unsigned order, size_t size)
{
if (addr) {
--
1.7.11.2
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