The patch titled Subject: mm: fork: fix kernel_stack memcg stats for various stack implementations has been added to the -mm tree. Its filename is mm-fork-fix-kernel_stack-memcg-stats-for-various-stack-implementations.patch
This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-fork-fix-kernel_stack-memcg-stat... and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-fork-fix-kernel_stack-memcg-stat...
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------------------------------------------------------ From: Roman Gushchin guro@fb.com Subject: mm: fork: fix kernel_stack memcg stats for various stack implementations
Depending on CONFIG_VMAP_STACK and the THREAD_SIZE / PAGE_SIZE ratio the space for task stacks can be allocated using __vmalloc_node_range(), alloc_pages_node() and kmem_cache_alloc_node(). In the first and the second cases page->mem_cgroup pointer is set, but in the third it's not: memcg membership of a slab page should be determined using the memcg_from_slab_page() function, which looks at page->slab_cache->memcg_params.memcg . In this case, using mod_memcg_page_state() (as in account_kernel_stack()) is incorrect: page->mem_cgroup pointer is NULL even for pages charged to a non-root memory cgroup.
It can lead to kernel_stack per-memcg counters permanently showing 0 on some architectures (depending on the configuration).
In order to fix it, let's introduce a mod_memcg_obj_state() helper, which takes a pointer to a kernel object as a first argument, uses mem_cgroup_from_obj() to get a RCU-protected memcg pointer and calls mod_memcg_state(). It allows to handle all possible configurations (CONFIG_VMAP_STACK and various THREAD_SIZE/PAGE_SIZE values) without spilling any memcg/kmem specifics into fork.c .
Note: this patch has been first posted as a part of the new slab controller patchset. This is a slightly updated version: the fixes tag has been added and the commit log was extended by the advice of Johannes Weiner. Because it's a fix that makes sense by itself, I'm re-posting it as a standalone patch.
Link: http://lkml.kernel.org/r/20200303233550.251375-1-guro@fb.com Fixes: 4d96ba353075 ("mm: memcg/slab: stop setting page->mem_cgroup pointer for slab pages") Signed-off-by: Roman Gushchin guro@fb.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Bharata B Rao bharata@linux.ibm.com Cc: Shakeel Butt shakeelb@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
include/linux/memcontrol.h | 5 +++++ kernel/fork.c | 4 ++-- mm/memcontrol.c | 11 +++++++++++ 3 files changed, 18 insertions(+), 2 deletions(-)
--- a/include/linux/memcontrol.h~mm-fork-fix-kernel_stack-memcg-stats-for-various-stack-implementations +++ a/include/linux/memcontrol.h @@ -695,6 +695,7 @@ static inline unsigned long lruvec_page_ void __mod_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx, int val); void __mod_lruvec_slab_state(void *p, enum node_stat_item idx, int val); +void mod_memcg_obj_state(void *p, int idx, int val);
static inline void mod_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx, int val) @@ -1123,6 +1124,10 @@ static inline void __mod_lruvec_slab_sta __mod_node_page_state(page_pgdat(page), idx, val); }
+static inline void mod_memcg_obj_state(void *p, int idx, int val) +{ +} + static inline unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order, gfp_t gfp_mask, --- a/kernel/fork.c~mm-fork-fix-kernel_stack-memcg-stats-for-various-stack-implementations +++ a/kernel/fork.c @@ -397,8 +397,8 @@ static void account_kernel_stack(struct mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB, THREAD_SIZE / 1024 * account);
- mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB, - account * (THREAD_SIZE / 1024)); + mod_memcg_obj_state(stack, MEMCG_KERNEL_STACK_KB, + account * (THREAD_SIZE / 1024)); } }
--- a/mm/memcontrol.c~mm-fork-fix-kernel_stack-memcg-stats-for-various-stack-implementations +++ a/mm/memcontrol.c @@ -777,6 +777,17 @@ void __mod_lruvec_slab_state(void *p, en rcu_read_unlock(); }
+void mod_memcg_obj_state(void *p, int idx, int val) +{ + struct mem_cgroup *memcg; + + rcu_read_lock(); + memcg = mem_cgroup_from_obj(p); + if (memcg) + mod_memcg_state(memcg, idx, val); + rcu_read_unlock(); +} + /** * __count_memcg_events - account VM events in a cgroup * @memcg: the memory cgroup _
Patches currently in -mm which might be from guro@fb.com are
mm-fork-fix-kernel_stack-memcg-stats-for-various-stack-implementations.patch mm-memcg-slab-introduce-mem_cgroup_from_obj.patch mm-memcg-slab-introduce-mem_cgroup_from_obj-v2.patch mm-kmem-cleanup-__memcg_kmem_charge_memcg-arguments.patch mm-kmem-cleanup-memcg_kmem_uncharge_memcg-arguments.patch mm-kmem-rename-memcg_kmem_uncharge-into-memcg_kmem_uncharge_page.patch mm-kmem-switch-to-nr_pages-in-__memcg_kmem_charge_memcg.patch mm-memcg-slab-cache-page-number-in-memcg_uncharge_slab.patch mm-kmem-rename-__memcg_kmem_uncharge_memcg-to-__memcg_kmem_uncharge.patch