From 7609385337a4feb6236e42dcd0df2185683ce839 Mon Sep 17 00:00:00 2001 From: xu xin Date: Thu, 28 Apr 2022 23:16:16 -0700 Subject: [PATCH] ksm: count ksm merging pages for each process Some applications or containers want to use KSM by calling madvise() to advise areas of address space to be MERGEABLE. But they may not know which applications are more likely to cause real merges in the deployment. If this patch is applied, it helps them know their corresponding number of merged pages, and then optimize their app code. As current KSM only counts the number of KSM merging pages(e.g. ksm_pages_sharing and ksm_pages_shared) of the whole system, we cannot see the more fine-grained KSM merging, for the upper application optimization, the merging area cannot be set easily according to the KSM page merging probability of each process. Therefore, it is necessary to add extra statistical means so that the upper level users can know the detailed KSM merging information of each process. We add a new proc file named as ksm_merging_pages under /proc// to indicate the involved ksm merging pages of this process. [akpm@linux-foundation.org: fix comment typo, remove BUG_ON()s] Link: https://lkml.kernel.org/r/20220325082318.2352853-1-xu.xin16@zte.com.cn Signed-off-by: xu xin Reported-by: kernel test robot Reviewed-by: Yang Yang Reviewed-by: Ran Xiaokai Reported-by: Zeal Robot Cc: Kees Cook Cc: Alexey Dobriyan Cc: Stephen Rothwell Cc: Ohhoon Kwon Cc: Matthew Wilcox (Oracle) Cc: Stephen Brennan Cc: Vlastimil Babka Cc: Feng Tang Cc: Yang Yang Cc: Ran Xiaokai Cc: Zeal Robot Signed-off-by: Andrew Morton --- fs/proc/base.c | 22 ++++++++++++++++++++++ include/linux/mm_types.h | 7 +++++++ mm/ksm.c | 8 ++++++++ 3 files changed, 37 insertions(+) diff --git a/fs/proc/base.c b/fs/proc/base.c index c1031843cc6a..8dfa36a99c74 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3154,6 +3154,22 @@ static int proc_pid_patch_state(struct seq_file *m, struct pid_namespace *ns, } #endif /* CONFIG_LIVEPATCH */ +#ifdef CONFIG_KSM +static int proc_pid_ksm_merging_pages(struct seq_file *m, struct pid_namespace *ns, + struct pid *pid, struct task_struct *task) +{ + struct mm_struct *mm; + + mm = get_task_mm(task); + if (mm) { + seq_printf(m, "%lu\n", mm->ksm_merging_pages); + mmput(mm); + } + + return 0; +} +#endif /* CONFIG_KSM */ + #ifdef CONFIG_STACKLEAK_METRICS static int proc_stack_depth(struct seq_file *m, struct pid_namespace *ns, struct pid *pid, struct task_struct *task) @@ -3285,6 +3301,9 @@ static const struct pid_entry tgid_base_stuff[] = { #ifdef CONFIG_SECCOMP_CACHE_DEBUG ONE("seccomp_cache", S_IRUSR, proc_pid_seccomp_cache), #endif +#ifdef CONFIG_KSM + ONE("ksm_merging_pages", S_IRUSR, proc_pid_ksm_merging_pages), +#endif }; static int proc_tgid_base_readdir(struct file *file, struct dir_context *ctx) @@ -3618,6 +3637,9 @@ static const struct pid_entry tid_base_stuff[] = { #ifdef CONFIG_SECCOMP_CACHE_DEBUG ONE("seccomp_cache", S_IRUSR, proc_pid_seccomp_cache), #endif +#ifdef CONFIG_KSM + ONE("ksm_merging_pages", S_IRUSR, proc_pid_ksm_merging_pages), +#endif }; static int proc_tid_base_readdir(struct file *file, struct dir_context *ctx) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 8834e38c06a4..87eddd509de2 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -654,6 +654,13 @@ struct mm_struct { #ifdef CONFIG_IOMMU_SVA u32 pasid; +#endif +#ifdef CONFIG_KSM + /* + * Represent how many pages of this process are involved in KSM + * merging. + */ + unsigned long ksm_merging_pages; #endif } __randomize_layout; diff --git a/mm/ksm.c b/mm/ksm.c index 063a48eeb5ee..94bb0f049806 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -638,6 +638,9 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node) ksm_pages_sharing--; else ksm_pages_shared--; + + rmap_item->mm->ksm_merging_pages--; + VM_BUG_ON(stable_node->rmap_hlist_len <= 0); stable_node->rmap_hlist_len--; put_anon_vma(rmap_item->anon_vma); @@ -785,6 +788,9 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) ksm_pages_sharing--; else ksm_pages_shared--; + + rmap_item->mm->ksm_merging_pages--; + VM_BUG_ON(stable_node->rmap_hlist_len <= 0); stable_node->rmap_hlist_len--; @@ -2007,6 +2013,8 @@ static void stable_tree_append(struct rmap_item *rmap_item, ksm_pages_sharing++; else ksm_pages_shared++; + + rmap_item->mm->ksm_merging_pages++; } /*