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(). [ v2: inverted test order to avoid a memcg_get leak, free_accounted_pages simplification ] [ v4: test for TIF_MEMDIE at newpage_charge ] Signed-off-by: Glauber Costa <glom...@parallels.com> Acked-by: Michal Hocko <mho...@suse.cz> Acked-by: Mel Gorman <mgor...@suse.de> Acked-by: Kamezawa Hiroyuki <kamezawa.hir...@jp.fujitsu.com> CC: Christoph Lameter <c...@linux.com> CC: Pekka Enberg <penb...@cs.helsinki.fi> CC: Johannes Weiner <han...@cmpxchg.org> CC: Suleiman Souhlal <sulei...@google.com> --- include/linux/gfp.h | 3 +++ mm/page_alloc.c | 35 +++++++++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+) diff --git a/include/linux/gfp.h b/include/linux/gfp.h index 9289d46..8f6fe34 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -362,6 +362,9 @@ 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 feddc7f..dcf33ad 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2595,6 +2595,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int migratetype = allocflags_to_migratetype(gfp_mask); unsigned int cpuset_mems_cookie; int alloc_flags = ALLOC_WMARK_LOW|ALLOC_CPUSET; + struct mem_cgroup *memcg = NULL; gfp_mask &= gfp_allowed_mask; @@ -2613,6 +2614,13 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, if (unlikely(!zonelist->_zonerefs->zone)) return NULL; + /* + * Will only have any effect when __GFP_KMEMCG is set. This is + * verified in the (always inline) callee + */ + if (!memcg_kmem_newpage_charge(gfp_mask, &memcg, order)) + return NULL; + retry_cpuset: cpuset_mems_cookie = get_mems_allowed(); @@ -2648,6 +2656,8 @@ out: if (unlikely(!put_mems_allowed(cpuset_mems_cookie) && !page)) goto retry_cpuset; + memcg_kmem_commit_charge(page, memcg, order); + return page; } EXPORT_SYMBOL(__alloc_pages_nodemask); @@ -2700,6 +2710,31 @@ 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_uncharge_page(page, order); + __free_pages(page, order); +} + +void free_accounted_pages(unsigned long addr, unsigned int order) +{ + if (addr != 0) { + VM_BUG_ON(!virt_addr_valid((void *)addr)); + __free_accounted_pages(virt_to_page((void *)addr), order); + } +} + static void *make_alloc_exact(unsigned long addr, unsigned order, size_t size) { if (addr) { -- 1.7.11.4 _______________________________________________ Devel mailing list Devel@openvz.org https://openvz.org/mailman/listinfo/devel