reduce m_start() cost...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

reduce m_start() cost...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Al Viro
1 parent f2ebb3a921
Showing 3 changed files with 23 additions and 4 deletions Side-by-side Diff
fs/mount.h
fs/namespace.c
fs/proc_namespace.c
@@ -10,7 +10,7 @@
 	struct user_namespace	*user_ns;
 	u64			seq;	/* Sequence number to prevent loops */
 	wait_queue_head_t poll;
-	int event;
+	u64 event;
 };
  
 struct mnt_pcp {
@@ -104,6 +104,9 @@
 	struct mnt_namespace *ns;
 	struct path root;
 	int (*show)(struct seq_file *, struct vfsmount *);
+	void *cached_mount;
+	u64 cached_event;
+	loff_t cached_index;
 };
  
 #define proc_mounts(p) (container_of((p), struct proc_mounts, m))
@@ -52,7 +52,7 @@
 }
 __setup("mphash_entries=", set_mphash_entries);
  
-static int event;
+static u64 event;
 static DEFINE_IDA(mnt_id_ida);
 static DEFINE_IDA(mnt_group_ida);
 static DEFINE_SPINLOCK(mnt_id_lock);
  
@@ -1100,14 +1100,29 @@
 	struct proc_mounts *p = proc_mounts(m);
  
 	down_read(&namespace_sem);
-	return seq_list_start(&p->ns->list, *pos);
+	if (p->cached_event == p->ns->event) {
+		void *v = p->cached_mount;
+		if (*pos == p->cached_index)
+			return v;
+		if (*pos == p->cached_index + 1) {
+			v = seq_list_next(v, &p->ns->list, &p->cached_index);
+			return p->cached_mount = v;
+		}
+	}
+
+	p->cached_event = p->ns->event;
+	p->cached_mount = seq_list_start(&p->ns->list, *pos);
+	p->cached_index = *pos;
+	return p->cached_mount;
 }
  
 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
 {
 	struct proc_mounts *p = proc_mounts(m);
  
-	return seq_list_next(v, &p->ns->list, pos);
+	p->cached_mount = seq_list_next(v, &p->ns->list, pos);
+	p->cached_index = *pos;
+	return p->cached_mount;
 }
  
 static void m_stop(struct seq_file *m, void *v)
@@ -267,6 +267,7 @@
 	p->root = root;
 	p->m.poll_event = ns->event;
 	p->show = show;
+	p->cached_event = ~0ULL;
  
 	return 0;
...	...	@@ -10,7 +10,7 @@
10	10	struct user_namespace *user_ns;
11	11	u64 seq; /* Sequence number to prevent loops */
12	12	wait_queue_head_t poll;
13		- int event;
	13	+ u64 event;
14	14	};
15	15
16	16	struct mnt_pcp {
...	...	@@ -104,6 +104,9 @@
104	104	struct mnt_namespace *ns;
105	105	struct path root;
106	106	int (show)(struct seq_file , struct vfsmount *);
	107	+ void *cached_mount;
	108	+ u64 cached_event;
	109	+ loff_t cached_index;
107	110	};
108	111
109	112	#define proc_mounts(p) (container_of((p), struct proc_mounts, m))
...	...	@@ -52,7 +52,7 @@
52	52	}
53	53	__setup("mphash_entries=", set_mphash_entries);
54	54
55		-static int event;
	55	+static u64 event;
56	56	static DEFINE_IDA(mnt_id_ida);
57	57	static DEFINE_IDA(mnt_group_ida);
58	58	static DEFINE_SPINLOCK(mnt_id_lock);
59	59
...	...	@@ -1100,14 +1100,29 @@
1100	1100	struct proc_mounts *p = proc_mounts(m);
1101	1101
1102	1102	down_read(&namespace_sem);
1103		- return seq_list_start(&p->ns->list, *pos);
	1103	+ if (p->cached_event == p->ns->event) {
	1104	+ void *v = p->cached_mount;
	1105	+ if (*pos == p->cached_index)
	1106	+ return v;
	1107	+ if (*pos == p->cached_index + 1) {
	1108	+ v = seq_list_next(v, &p->ns->list, &p->cached_index);
	1109	+ return p->cached_mount = v;
	1110	+ }
	1111	+ }
	1112	+
	1113	+ p->cached_event = p->ns->event;
	1114	+ p->cached_mount = seq_list_start(&p->ns->list, *pos);
	1115	+ p->cached_index = *pos;
	1116	+ return p->cached_mount;
1104	1117	}
1105	1118
1106	1119	static void m_next(struct seq_file m, void v, loff_t pos)
1107	1120	{
1108	1121	struct proc_mounts *p = proc_mounts(m);
1109	1122
1110		- return seq_list_next(v, &p->ns->list, pos);
	1123	+ p->cached_mount = seq_list_next(v, &p->ns->list, pos);
	1124	+ p->cached_index = *pos;
	1125	+ return p->cached_mount;
1111	1126	}
1112	1127
1113	1128	static void m_stop(struct seq_file m, void v)
...	...	@@ -267,6 +267,7 @@
267	267	p->root = root;
268	268	p->m.poll_event = ns->event;
269	269	p->show = show;
	270	+ p->cached_event = ~0ULL;
270	271
271	272	return 0;
272	273