From 354ed597442952fb680c9cafc7e4eb8a76f9514c Mon Sep 17 00:00:00 2001 From: Yu Zhao Date: Sun, 18 Sep 2022 02:00:07 -0600 Subject: mm: multi-gen LRU: kill switch MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add /sys/kernel/mm/lru_gen/enabled as a kill switch. Components that can be disabled include: 0x0001: the multi-gen LRU core 0x0002: walking page table, when arch_has_hw_pte_young() returns true 0x0004: clearing the accessed bit in non-leaf PMD entries, when CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG=y [yYnN]: apply to all the components above E.g., echo y >/sys/kernel/mm/lru_gen/enabled cat /sys/kernel/mm/lru_gen/enabled 0x0007 echo 5 >/sys/kernel/mm/lru_gen/enabled cat /sys/kernel/mm/lru_gen/enabled 0x0005 NB: the page table walks happen on the scale of seconds under heavy memory pressure, in which case the mmap_lock contention is a lesser concern, compared with the LRU lock contention and the I/O congestion. So far the only well-known case of the mmap_lock contention happens on Android, due to Scudo [1] which allocates several thousand VMAs for merely a few hundred MBs. The SPF and the Maple Tree also have provided their own assessments [2][3]. However, if walking page tables does worsen the mmap_lock contention, the kill switch can be used to disable it. In this case the multi-gen LRU will suffer a minor performance degradation, as shown previously. Clearing the accessed bit in non-leaf PMD entries can also be disabled, since this behavior was not tested on x86 varieties other than Intel and AMD. [1] https://source.android.com/devices/tech/debug/scudo [2] https://lore.kernel.org/r/20220128131006.67712-1-michel@lespinasse.org/ [3] https://lore.kernel.org/r/20220426150616.3937571-1-Liam.Howlett@oracle.com/ Link: https://lkml.kernel.org/r/20220918080010.2920238-11-yuzhao@google.com Signed-off-by: Yu Zhao Acked-by: Brian Geffon Acked-by: Jan Alexander Steffens (heftig) Acked-by: Oleksandr Natalenko Acked-by: Steven Barrett Acked-by: Suleiman Souhlal Tested-by: Daniel Byrne Tested-by: Donald Carr Tested-by: Holger Hoffstätte Tested-by: Konstantin Kharlamov Tested-by: Shuang Zhai Tested-by: Sofia Trinh Tested-by: Vaibhav Jain Cc: Andi Kleen Cc: Aneesh Kumar K.V Cc: Barry Song Cc: Catalin Marinas Cc: Dave Hansen Cc: Hillf Danton Cc: Jens Axboe Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Linus Torvalds Cc: Matthew Wilcox Cc: Mel Gorman Cc: Miaohe Lin Cc: Michael Larabel Cc: Michal Hocko Cc: Mike Rapoport Cc: Mike Rapoport Cc: Peter Zijlstra Cc: Qi Zheng Cc: Tejun Heo Cc: Vlastimil Babka Cc: Will Deacon Signed-off-by: Andrew Morton --- include/linux/cgroup.h | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) (limited to 'include/linux/cgroup.h') diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index ac5d0515680e..9179463c3c9f 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -432,6 +432,18 @@ static inline void cgroup_put(struct cgroup *cgrp) css_put(&cgrp->self); } +extern struct mutex cgroup_mutex; + +static inline void cgroup_lock(void) +{ + mutex_lock(&cgroup_mutex); +} + +static inline void cgroup_unlock(void) +{ + mutex_unlock(&cgroup_mutex); +} + /** * task_css_set_check - obtain a task's css_set with extra access conditions * @task: the task to obtain css_set for @@ -446,7 +458,6 @@ static inline void cgroup_put(struct cgroup *cgrp) * as locks used during the cgroup_subsys::attach() methods. */ #ifdef CONFIG_PROVE_RCU -extern struct mutex cgroup_mutex; extern spinlock_t css_set_lock; #define task_css_set_check(task, __c) \ rcu_dereference_check((task)->cgroups, \ @@ -708,6 +719,8 @@ struct cgroup; static inline u64 cgroup_id(const struct cgroup *cgrp) { return 1; } static inline void css_get(struct cgroup_subsys_state *css) {} static inline void css_put(struct cgroup_subsys_state *css) {} +static inline void cgroup_lock(void) {} +static inline void cgroup_unlock(void) {} static inline int cgroup_attach_task_all(struct task_struct *from, struct task_struct *t) { return 0; } static inline int cgroupstats_build(struct cgroupstats *stats, -- cgit v1.2.3-59-g8ed1b