[PATCH v2] 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.

Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Yang Yang <yang.yang29@zte.com.cn>
Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
---
 fs/proc/base.c           | 22 ++++++++++++++++++++++
 include/linux/mm_types.h |  8 ++++++++
 mm/ksm.c                 | 11 +++++++++++
 3 files changed, 41 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index d654ce7..5c8feef 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3155,6 +3155,22 @@ 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)
@@ -3286,6 +3302,9 @@ 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)
@@ -3619,6 +3638,9 @@ 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 9db36dc..4d98bd5 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -633,6 +633,14 @@ struct mm_struct {
 #ifdef CONFIG_IOMMU_SUPPORT
 		u32 pasid;
 #endif
+
+#ifdef CONFIG_KSM
+		/*
+		 * Represet 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 c20bd4d..5889733 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -638,6 +638,10 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node)
 			ksm_pages_sharing--;
 		else
 			ksm_pages_shared--;
+
+		BUG_ON(rmap_item->mm == NULL);
+		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 +789,10 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item)
 			ksm_pages_sharing--;
 		else
 			ksm_pages_shared--;
+
+		BUG_ON(rmap_item->mm == NULL);
+		rmap_item->mm->ksm_merging_pages--;
+
 		VM_BUG_ON(stable_node->rmap_hlist_len <= 0);
 		stable_node->rmap_hlist_len--;
 
@@ -2020,6 +2028,9 @@ static void stable_tree_append(struct rmap_item *rmap_item,
 		ksm_pages_sharing++;
 	else
 		ksm_pages_shared++;
+
+	BUG_ON(rmap_item->mm == NULL);
+	rmap_item->mm->ksm_merging_pages++;
 }
 
 /*
-- 
2.15.2