| Message ID | 20200127173453.2089565-9-guro@fb.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | The new cgroup slab memory controller | expand |
On Mon, Jan 27, 2020 at 09:34:33AM -0800, Roman Gushchin wrote: > 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. > > 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 . The change looks good to me, but it sounds like this is a bug with actual consequences to userspace. Can you elaborate on that in the changelog please? Maybe add a Fixes: line, if applicable?
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 24c50d004c46..1b4150ff64be 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -695,6 +695,7 @@ static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec, 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_state(void *p, enum node_stat_item idx, __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, diff --git a/kernel/fork.c b/kernel/fork.c index 4dad271ee28e..d8d1ccc7a40e 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -397,8 +397,8 @@ static void account_kernel_stack(struct task_struct *tsk, int account) 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)); } } diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 43010471621c..2bdc1ae5402a 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -774,6 +774,17 @@ void __mod_lruvec_slab_state(void *p, enum node_stat_item idx, int val) 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
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. 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 . Signed-off-by: Roman Gushchin <guro@fb.com> --- include/linux/memcontrol.h | 5 +++++ kernel/fork.c | 4 ++-- mm/memcontrol.c | 11 +++++++++++ 3 files changed, 18 insertions(+), 2 deletions(-)