From 37d5985c003daab138a72dd4af9853b396d91c26 Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Sat, 17 Oct 2020 16:13:50 -0700 Subject: mm: kmem: prepare remote memcg charging infra for interrupt contexts Remote memcg charging API uses current->active_memcg to store the currently active memory cgroup, which overwrites the memory cgroup of the current process. It works well for normal contexts, but doesn't work for interrupt contexts: indeed, if an interrupt occurs during the execution of a section with an active memcg set, all allocations inside the interrupt will be charged to the active memcg set (given that we'll enable accounting for allocations from an interrupt context). But because the interrupt might have no relation to the active memcg set outside, it's obviously wrong from the accounting prospective. To resolve this problem, let's add a global percpu int_active_memcg variable, which will be used to store an active memory cgroup which will be used from interrupt contexts. set_active_memcg() will transparently use current->active_memcg or int_active_memcg depending on the context. To make the read part simple and transparent for the caller, let's introduce two new functions: - struct mem_cgroup *active_memcg(void), - struct mem_cgroup *get_active_memcg(void). They are returning the active memcg if it's set, hiding all implementation details: where to get it depending on the current context. Signed-off-by: Roman Gushchin Signed-off-by: Andrew Morton Reviewed-by: Shakeel Butt Cc: Johannes Weiner Cc: Michal Hocko Link: http://lkml.kernel.org/r/20200827225843.1270629-4-guro@fb.com Signed-off-by: Linus Torvalds --- include/linux/sched/mm.h | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index 1a80fb128e74..d5ece7a9a403 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -279,6 +279,7 @@ static inline void memalloc_nocma_restore(unsigned int flags) #endif #ifdef CONFIG_MEMCG +DECLARE_PER_CPU(struct mem_cgroup *, int_active_memcg); /** * set_active_memcg - Starts the remote memcg charging scope. * @memcg: memcg to charge. @@ -293,8 +294,16 @@ static inline void memalloc_nocma_restore(unsigned int flags) static inline struct mem_cgroup * set_active_memcg(struct mem_cgroup *memcg) { - struct mem_cgroup *old = current->active_memcg; - current->active_memcg = memcg; + struct mem_cgroup *old; + + if (in_interrupt()) { + old = this_cpu_read(int_active_memcg); + this_cpu_write(int_active_memcg, memcg); + } else { + old = current->active_memcg; + current->active_memcg = memcg; + } + return old; } #else -- cgit v1.2.3