[PATCH 1/2] VFS: New /proc file /proc/self/mountstats

[PATCH 1/2] VFS: New /proc file /proc/self/mountstats

[Chuck Lever]

 Create a new file under /proc/self, called mountstats, where mounted file
 systems can export information (configuration options, performance counters,
 and so on).  Use a mechanism similar to /proc/mounts and s_ops->show_options.

 This mechanism does not violate namespace security, and is safe to use while
 other processes are unmounting file systems.

 Version: Mon, 14 Mar 2005 17:06:04 -0500
 
 Signed-off-by: Chuck Lever <cel@netapp.com>
---
 
 fs/namespace.c     |   66 +++++++++++++++++++++++++++++++++++++++++++++
 fs/proc/base.c     |   40 +++++++++++++++++++++++++++
 include/linux/fs.h |    1 
 3 files changed, 107 insertions(+)
 
 
diff -X /home/cel/src/linux/dont-diff -Naurp 00-stock/fs/namespace.c 01-mountstats/fs/namespace.c
--- 00-stock/fs/namespace.c	2005-03-02 02:38:13.000000000 -0500
+++ 01-mountstats/fs/namespace.c	2005-03-14 15:24:51.565085000 -0500
@@ -265,6 +265,72 @@ struct seq_operations mounts_op = {
 	.show	= show_vfsmnt
 };
 
+/* iterator */
+static void *ms_start(struct seq_file *m, loff_t *pos)
+{
+	struct namespace *n = m->private;
+	struct list_head *p;
+	loff_t l = *pos;
+
+	down_read(&n->sem);
+	list_for_each(p, &n->list)
+		if (!l--)
+			return list_entry(p, struct vfsmount, mnt_list);
+	return NULL;
+}
+
+static void *ms_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct namespace *n = m->private;
+	struct list_head *p = ((struct vfsmount *)v)->mnt_list.next;
+	(*pos)++;
+	return p==&n->list ? NULL : list_entry(p, struct vfsmount, mnt_list);
+}
+
+static void ms_stop(struct seq_file *m, void *v)
+{
+	struct namespace *n = m->private;
+	up_read(&n->sem);
+}
+
+static int show_vfsstat(struct seq_file *m, void *v)
+{
+	struct vfsmount *mnt = v;
+	int err = 0;
+
+	/* device */
+	if (mnt->mnt_devname) {
+		seq_puts(m, "device ");
+		mangle(m, mnt->mnt_devname);
+	} else
+		seq_puts(m, "no device");
+
+	/* mount point */
+	seq_puts(m, " mounted on ");
+	seq_path(m, mnt, mnt->mnt_root, " \t\n\\");
+	seq_putc(m, ' ');
+
+	/* file system type */
+	seq_puts(m, "with fstype ");
+	mangle(m, mnt->mnt_sb->s_type->name);
+
+	/* optional statistics */
+	if (mnt->mnt_sb->s_op->show_stats) {
+		seq_putc(m, ' ');
+		err = mnt->mnt_sb->s_op->show_stats(m, mnt);
+	}
+
+	seq_putc(m, '\n');
+	return err;
+}
+
+struct seq_operations mountstats_op = {
+	.start	= ms_start,
+	.next	= ms_next,
+	.stop	= ms_stop,
+	.show	= show_vfsstat,
+};
+
 /**
  * may_umount_tree - check if a mount tree is busy
  * @mnt: root of mount tree
diff -X /home/cel/src/linux/dont-diff -Naurp 00-stock/fs/proc/base.c 01-mountstats/fs/proc/base.c
--- 00-stock/fs/proc/base.c	2005-03-02 02:38:12.000000000 -0500
+++ 01-mountstats/fs/proc/base.c	2005-03-14 15:24:51.571085000 -0500
@@ -60,6 +60,7 @@ enum pid_directory_inos {
 	PROC_TGID_STATM,
 	PROC_TGID_MAPS,
 	PROC_TGID_MOUNTS,
+	PROC_TGID_MOUNTSTATS,
 	PROC_TGID_WCHAN,
 #ifdef CONFIG_SCHEDSTATS
 	PROC_TGID_SCHEDSTAT,
@@ -91,6 +92,7 @@ enum pid_directory_inos {
 	PROC_TID_STATM,
 	PROC_TID_MAPS,
 	PROC_TID_MOUNTS,
+	PROC_TID_MOUNTSTATS,
 	PROC_TID_WCHAN,
 #ifdef CONFIG_SCHEDSTATS
 	PROC_TID_SCHEDSTAT,
@@ -134,6 +136,7 @@ static struct pid_entry tgid_base_stuff[
 	E(PROC_TGID_ROOT,      "root",    S_IFLNK|S_IRWXUGO),
 	E(PROC_TGID_EXE,       "exe",     S_IFLNK|S_IRWXUGO),
 	E(PROC_TGID_MOUNTS,    "mounts",  S_IFREG|S_IRUGO),
+	E(PROC_TGID_MOUNTSTATS, "mountstats", S_IFREG|S_IRUGO),
 #ifdef CONFIG_SECURITY
 	E(PROC_TGID_ATTR,      "attr",    S_IFDIR|S_IRUGO|S_IXUGO),
 #endif
@@ -164,6 +167,7 @@ static struct pid_entry tid_base_stuff[]
 	E(PROC_TID_ROOT,       "root",    S_IFLNK|S_IRWXUGO),
 	E(PROC_TID_EXE,        "exe",     S_IFLNK|S_IRWXUGO),
 	E(PROC_TID_MOUNTS,     "mounts",  S_IFREG|S_IRUGO),
+	E(PROC_TID_MOUNTSTATS, "mountstats", S_IFREG|S_IRUGO),
 #ifdef CONFIG_SECURITY
 	E(PROC_TID_ATTR,       "attr",    S_IFDIR|S_IRUGO|S_IXUGO),
 #endif
@@ -528,6 +532,38 @@ static struct file_operations proc_mount
 	.release	= mounts_release,
 };
 
+extern struct seq_operations mountstats_op;
+static int mountstats_open(struct inode *inode, struct file *file)
+{
+	struct task_struct *task = proc_task(inode);
+	int ret = seq_open(file, &mountstats_op);
+
+	if (!ret) {
+		struct seq_file *m = file->private_data;
+		struct namespace *namespace;
+		task_lock(task);
+		namespace = task->namespace;
+		if (namespace)
+			get_namespace(namespace);
+		task_unlock(task);
+
+		if (namespace)
+			m->private = namespace;
+		else {
+			seq_release(inode, file);
+			ret = -EINVAL;
+		}
+	}
+	return ret;
+}
+
+static struct file_operations proc_mountstats_operations = {
+	.open		= mountstats_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= mounts_release,
+};
+
 #define PROC_BLOCK_SIZE	(3*1024)		/* 4K page size but our output routines use some slack for overruns */
 
 static ssize_t proc_info_read(struct file * file, char __user * buf,
@@ -1447,6 +1483,10 @@ static struct dentry *proc_pident_lookup
 		case PROC_TGID_MOUNTS:
 			inode->i_fop = &proc_mounts_operations;
 			break;
+		case PROC_TID_MOUNTSTATS:
+		case PROC_TGID_MOUNTSTATS:
+			inode->i_fop = &proc_mountstats_operations;
+			break;
 #ifdef CONFIG_SECURITY
 		case PROC_TID_ATTR:
 			inode->i_nlink = 2;
diff -X /home/cel/src/linux/dont-diff -Naurp 00-stock/include/linux/fs.h 01-mountstats/include/linux/fs.h
--- 00-stock/include/linux/fs.h	2005-03-02 02:37:50.000000000 -0500
+++ 01-mountstats/include/linux/fs.h	2005-03-14 15:24:51.598084000 -0500
@@ -1008,6 +1008,7 @@ struct super_operations {
 	void (*umount_begin) (struct super_block *);
 
 	int (*show_options)(struct seq_file *, struct vfsmount *);
+	int (*show_stats)(struct seq_file *, struct vfsmount *);
 
 	ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
 	ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);

Re: [PATCH 1/2] VFS: New /proc file /proc/self/mountstats

[stark-DPNOqEs/LNQ]

Chuck Lever <cel <at> citi.umich.edu> writes:

> Create a new file under /proc/self, called mountstats, where mounted file
> systems can export information (configuration options, performance counters,
> and so on). Use a mechanism similar to /proc/mounts and s_ops->show_options.

I'm using this file to dump data into our performance metrics database along
with all the other counters from snmp and other sources. This lets us
calculate things like the average number of requests pending, average latency
per request over time.

But I have a few questions about the meaning of the values and they don't seem
to be documented outside the comments in the source. 

In particular is it an invariant that execution = rtt + queue? Or is execution
including some additional overhead other than the server and network
congestion? Or is there something more subtle going on and these values aren't
related in the way I'm imagining at all?

And where can I read about the meaning of bad_xids, req_u, and bklog_u? What
do they mean?

Also, connect_time, idle_time, req_u, and bklog_u are instantaneous samples
("guages" so to speak), not integrated over time right? So they can't be used
to calculate any aggregates?
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