[PATCH linux-next] ksm: Count ksm-merging pages for each process

[cgel.zte@gmail.com]

From: xu xin <xu.xin16@zte.com.cn>

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/<pid>/
to indicate the involved ksm merging pages of this process.

Thanks-to: Yang Yang <yang.yang29@zte.com.cn>
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
---
 fs/proc/base.c        | 15 +++++++++++++++
 include/linux/sched.h |  5 +++++
 mm/ksm.c              | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 76bf1aa3cfe8..b044535df0d2 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3155,6 +3155,15 @@ static int proc_pid_patch_state(struct seq_file *m, struct pid_namespace *ns,
 }
 #endif /* CONFIG_LIVEPATCH */
 
+#if defined(CONFIG_KSM) && defined(CONFIG_MEMCG)
+static int proc_pid_ksm_merging_pages(struct seq_file *m, struct pid_namespace *ns,
+				struct pid *pid, struct task_struct *task)
+{
+	seq_printf(m, "%lu\n", task->ksm_merging_pages);
+	return 0;
+}
+#endif /* CONFIG_KSM and CONFIG_MEMCG */
+
 #ifdef CONFIG_STACKLEAK_METRICS
 static int proc_stack_depth(struct seq_file *m, struct pid_namespace *ns,
 				struct pid *pid, struct task_struct *task)
@@ -3286,6 +3295,9 @@ static const struct pid_entry tgid_base_stuff[] = {
 #ifdef CONFIG_SECCOMP_CACHE_DEBUG
 	ONE("seccomp_cache", S_IRUSR, proc_pid_seccomp_cache),
 #endif
+#if defined(CONFIG_KSM) && defined(CONFIG_MEMCG)
+	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)
@@ -3619,6 +3631,9 @@ static const struct pid_entry tid_base_stuff[] = {
 #ifdef CONFIG_SECCOMP_CACHE_DEBUG
 	ONE("seccomp_cache", S_IRUSR, proc_pid_seccomp_cache),
 #endif
+#if defined(CONFIG_KSM) && defined(CONFIG_MEMCG)
+	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/sched.h b/include/linux/sched.h
index ad710b3f664e..d092cf1a100d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1346,6 +1346,11 @@ struct task_struct {
 	unsigned int			kasan_depth;
 #endif
 
+#if defined(CONFIG_KSM) && defined(CONFIG_MEMCG)
+	unsigned long ksm_merging_pages;
+#endif
+
+
 #ifdef CONFIG_KCSAN
 	struct kcsan_ctx		kcsan_ctx;
 #ifdef CONFIG_TRACE_IRQFLAGS
diff --git a/mm/ksm.c b/mm/ksm.c
index 063a48eeb5ee..c79e7ff278bd 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -629,6 +629,9 @@ static inline void free_stable_node_chain(struct stable_node *chain,
 static void remove_node_from_stable_tree(struct stable_node *stable_node)
 {
 	struct rmap_item *rmap_item;
+#ifdef CONFIG_MEMCG
+	struct task_struct *owner;
+#endif
 
 	/* check it's not STABLE_NODE_CHAIN or negative */
 	BUG_ON(stable_node->rmap_hlist_len < 0);
@@ -638,6 +641,14 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node)
 			ksm_pages_sharing--;
 		else
 			ksm_pages_shared--;
+
+#ifdef CONFIG_MEMCG /*Condition of mm_struct with owner*/
+		BUG_ON(rmap_item->mm == NULL);
+		owner = rmap_item->mm->owner;
+		/* In case that the process of mm may be killed or exit */
+		if (owner)
+			owner->ksm_merging_pages--;
+#endif
 		VM_BUG_ON(stable_node->rmap_hlist_len <= 0);
 		stable_node->rmap_hlist_len--;
 		put_anon_vma(rmap_item->anon_vma);
@@ -771,6 +782,9 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item)
 	if (rmap_item->address & STABLE_FLAG) {
 		struct stable_node *stable_node;
 		struct page *page;
+#ifdef CONFIG_MEMCG
+		struct task_struct *owner;
+#endif
 
 		stable_node = rmap_item->head;
 		page = get_ksm_page(stable_node, GET_KSM_PAGE_LOCK);
@@ -785,6 +799,14 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item)
 			ksm_pages_sharing--;
 		else
 			ksm_pages_shared--;
+
+#ifdef CONFIG_MEMCG /*Condition of mm_struct with owner*/
+		BUG_ON(rmap_item->mm == NULL);
+		owner = rmap_item->mm->owner;
+		/* In case that the process of mm may be killed or exit */
+		if (owner)
+			owner->ksm_merging_pages--;
+#endif
 		VM_BUG_ON(stable_node->rmap_hlist_len <= 0);
 		stable_node->rmap_hlist_len--;
 
@@ -1981,6 +2003,9 @@ static void stable_tree_append(struct rmap_item *rmap_item,
 			       struct stable_node *stable_node,
 			       bool max_page_sharing_bypass)
 {
+#ifdef CONFIG_MEMCG
+	struct task_struct *owner;
+#endif
 	/*
 	 * rmap won't find this mapping if we don't insert the
 	 * rmap_item in the right stable_node
@@ -2007,6 +2032,14 @@ static void stable_tree_append(struct rmap_item *rmap_item,
 		ksm_pages_sharing++;
 	else
 		ksm_pages_shared++;
+
+#ifdef CONFIG_MEMCG /*Condition of mm_struct with owner*/
+	BUG_ON(rmap_item->mm == NULL);
+	owner = rmap_item->mm->owner;
+	/* In case that the process of mm may be killed or exit */
+	if (owner)
+		owner->ksm_merging_pages++;
+#endif
 }
 
 /*
-- 
2.25.1