[PATCH v6 01/11] VFS hot tracking: Define basic data structures and functions

Zhi Yong Wu
2013-11-06T13:51:45Z

From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>

This patch includes the basic data structure and functions needed for
VFS hot tracking.

It adds hot_inode_tree struct to keep track of frequently accessed
files, and is keyed by {inode, offset}. Trees contain hot_inode_items
representing those files and hot_range_items representing ranges in that
file.

It defines a data structure hot_info, which is associated with a mounted
filesystem, and will be used to store the inode tree and range tree for
hot items pertaining to that filesystem.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
fs/Makefile | 2 +-
fs/dcache.c | 2 +
fs/hot_tracking.c | 227 +++++++++++++++++++++++++++++++++++++++++++
fs/hot_tracking.h | 23 +++++
include/linux/fs.h | 4 +
include/linux/hot_tracking.h | 66 +++++++++++++
include/uapi/linux/fs.h | 1 +
7 files changed, 324 insertions(+), 1 deletion(-)
create mode 100644 fs/hot_tracking.c
create mode 100644 fs/hot_tracking.h
create mode 100644 include/linux/hot_tracking.h

diff --git a/fs/Makefile b/fs/Makefile
index 4fe6df3..5f9b8f1 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -11,7 +11,7 @@ obj-y := open.o read_write.o file_table.o super.o \
attr.o bad_inode.o file.o filesystems.o namespace.o \
seq_file.o xattr.o libfs.o fs-writeback.o \
pnode.o splice.o sync.o utimes.o \
- stack.o fs_struct.o statfs.o
+ stack.o fs_struct.o statfs.o hot_tracking.o

ifeq ($(CONFIG_BLOCK),y)
obj-y += buffer.o bio.o block_dev.o direct-io.o mpage.o ioprio.o
diff --git a/fs/dcache.c b/fs/dcache.c
index ae6ebb8..40dfd63 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -40,6 +40,7 @@
#include <linux/list_lru.h>
#include "internal.h"
#include "mount.h"
+#include "hot_tracking.h"

/*
* Usage:
@@ -3437,4 +3438,5 @@ void __init vfs_caches_init(unsigned long mempages)
mnt_init();
bdev_cache_init();
chrdev_init();
+ hot_cache_init();
}
diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
new file mode 100644
index 0000000..25e7858
--- /dev/null
+++ b/fs/hot_tracking.c
@@ -0,0 +1,227 @@
+/*
+ * fs/hot_tracking.c
+ *
+ * Copyright (C) 2013 IBM Corp. All rights reserved.
+ * Written by Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ */
+
+#include <linux/list.h>
+#include <linux/err.h>
+#include <linux/spinlock.h>
+#include "hot_tracking.h"
+
+/* kmem_cache pointers for slab caches */
+static struct kmem_cache *hot_inode_item_cachep __read_mostly;
+static struct kmem_cache *hot_range_item_cachep __read_mostly;
+
+static void hot_range_item_init(struct hot_range_item *hr,
+ struct hot_inode_item *he, loff_t start)
+{
+ kref_init(&hr->refs);
+ hr->start = start;
+ hr->len = 1 << RANGE_BITS;
+ hr->hot_inode = he;
+}
+
+static void hot_range_item_free_cb(struct rcu_head *head)
+{
+ struct hot_range_item *hr = container_of(head,
+ struct hot_range_item, rcu);
+
+ kmem_cache_free(hot_range_item_cachep, hr);
+}
+
+static void hot_range_item_free(struct kref *kref)
+{
+ struct hot_range_item *hr = container_of(kref,
+ struct hot_range_item, refs);
+
+ rb_erase(&hr->rb_node, &hr->hot_inode->hot_range_tree);
+
+ call_rcu(&hr->rcu, hot_range_item_free_cb);
+}
+
+static void hot_range_item_get(struct hot_range_item *hr)
+{
+ kref_get(&hr->refs);
+}
+
+/*
+ * Drops the reference out on hot_range_item by one
+ * and free the structure if the reference count hits zero
+ */
+static void hot_range_item_put(struct hot_range_item *hr)
+{
+ kref_put(&hr->refs, hot_range_item_free);
+}
+
+/*
+ * Free the entire hot_range_tree.
+ */
+static void hot_range_tree_free(struct hot_inode_item *he)
+{
+ struct rb_node *node;
+ struct hot_range_item *hr;
+
+ /* Free hot inode and range trees on fs root */
+ spin_lock(&he->i_lock);
+ node = rb_first(&he->hot_range_tree);
+ while (node) {
+ hr = rb_entry(node, struct hot_range_item, rb_node);
+ node = rb_next(node);
+ hot_range_item_put(hr);
+ }
+ spin_unlock(&he->i_lock);
+}
+
+static void hot_inode_item_init(struct hot_inode_item *he,
+ struct hot_info *root, u64 ino)
+{
+ kref_init(&he->refs);
+ he->ino = ino;
+ he->hot_root = root;
+ spin_lock_init(&he->i_lock);
+}
+
+static void hot_inode_item_free_cb(struct rcu_head *head)
+{
+ struct hot_inode_item *he = container_of(head,
+ struct hot_inode_item, rcu);
+
+ kmem_cache_free(hot_inode_item_cachep, he);
+}
+
+static void hot_inode_item_free(struct kref *kref)
+{
+ struct hot_inode_item *he = container_of(kref,
+ struct hot_inode_item, refs);
+
+ rb_erase(&he->rb_node, &he->hot_root->hot_inode_tree);
+ hot_range_tree_free(he);
+
+ call_rcu(&he->rcu, hot_inode_item_free_cb);
+}
+
+static void hot_inode_item_get(struct hot_inode_item *he)
+{
+ kref_get(&he->refs);
+}
+
+/*
+ * Drops the reference out on hot_inode_item by one
+ * and free the structure if the reference count hits zero
+ */
+void hot_inode_item_put(struct hot_inode_item *he)
+{
+ kref_put(&he->refs, hot_inode_item_free);
+}
+
+/*
+ * Initialize kmem cache for hot_inode_item and hot_range_item.
+ */
+void __init hot_cache_init(void)
+{
+ hot_inode_item_cachep = KMEM_CACHE(hot_inode_item,
+ SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD);
+ if (!hot_inode_item_cachep)
+ return;
+
+ hot_range_item_cachep = KMEM_CACHE(hot_range_item,
+ SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD);
+ if (!hot_range_item_cachep)
+ kmem_cache_destroy(hot_inode_item_cachep);
+}
+
+static struct hot_info *hot_tree_init(struct super_block *sb)
+{
+ struct hot_info *root;
+ int i, j;
+
+ root = kzalloc(sizeof(struct hot_info), GFP_NOFS);
+ if (!root) {
+ printk(KERN_ERR "%s: Failed to malloc memory for "
+ "hot_info\n", __func__);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ root->hot_inode_tree = RB_ROOT;
+ spin_lock_init(&root->t_lock);
+
+ return root;
+}
+
+/*
+ * Frees the entire hot tree.
+ */
+static void hot_tree_exit(struct hot_info *root)
+{
+ struct hot_inode_item *he;
+ struct rb_node *node;
+
+ spin_lock(&root->t_lock);
+ node = rb_first(&root->hot_inode_tree);
+ while (node) {
+ he = rb_entry(node, struct hot_inode_item, rb_node);
+ node = rb_next(node);
+ hot_inode_item_put(he);
+ }
+ spin_unlock(&root->t_lock);
+}
+
+/*
+ * Initialize the data structures for hot tracking.
+ * This function will be called by *_fill_super()
+ * when filesystem is mounted.
+ */
+int hot_track_init(struct super_block *sb)
+{
+ struct hot_info *root;
+ int ret = 0;
+
+ if (!hot_inode_item_cachep || !hot_range_item_cachep) {
+ ret = -ENOMEM;
+ goto err;
+ }
+
+ root = hot_tree_init(sb);
+ if (IS_ERR(root)) {
+ ret = PTR_ERR(root);
+ goto err;
+ }
+
+ sb->s_hot_root = root;
+ sb->s_flags |= MS_HOTTRACK;
+
+ printk(KERN_INFO "VFS: Turning on hot tracking\n");
+
+ return ret;
+
+err:
+ sb->s_hot_root = NULL;
+
+ printk(KERN_ERR "VFS: Fail to turn on hot tracking\n");
+
+ return ret;
+}
+EXPORT_SYMBOL(hot_track_init);
+
+/*
+ * This function will be called by *_put_super()
+ * when filesystem is umounted, or also by *_fill_super()
+ * in some exceptional cases.
+ */
+void hot_track_exit(struct super_block *sb)
+{
+ struct hot_info *root = sb->s_hot_root;
+
+ sb->s_hot_root = NULL;
+ sb->s_flags &= ~MS_HOTTRACK;
+ hot_tree_exit(root);
+ rcu_barrier();
+ kfree(root);
+}
+EXPORT_SYMBOL(hot_track_exit);
diff --git a/fs/hot_tracking.h b/fs/hot_tracking.h
new file mode 100644
index 0000000..51d829e
--- /dev/null
+++ b/fs/hot_tracking.h
@@ -0,0 +1,23 @@
+/*
+ * fs/hot_tracking.h
+ *
+ * Copyright (C) 2013 IBM Corp. All rights reserved.
+ * Written by Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ */
+
+#ifndef __HOT_TRACKING__
+#define __HOT_TRACKING__
+
+#include <linux/hot_tracking.h>
+
+/* size of sub-file ranges */
+#define RANGE_BITS 20
+
+void __init hot_cache_init(void);
+void hot_inode_item_put(struct hot_inode_item *he);
+
+#endif /* __HOT_TRACKING__ */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3f40547..8c8c40d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -29,6 +29,7 @@
#include <linux/lockdep.h>
#include <linux/percpu-rwsem.h>
#include <linux/blk_types.h>
+#include <linux/hot_tracking.h>

#include <asm/byteorder.h>
#include <uapi/linux/fs.h>
@@ -1324,6 +1325,9 @@ struct super_block {
/* AIO completions deferred from interrupt context */
struct workqueue_struct *s_dio_done_wq;

+ /* Hot data tracking*/
+ struct hot_info *s_hot_root;
+
/*
* Keep the lru lists last in the structure so they always sit on their
* own individual cachelines.
diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
new file mode 100644
index 0000000..91633db
--- /dev/null
+++ b/include/linux/hot_tracking.h
@@ -0,0 +1,66 @@
+/*
+ * include/linux/hot_tracking.h
+ *
+ * This file has definitions for VFS hot tracking
+ * structures etc.
+ *
+ * Copyright (C) 2013 IBM Corp. All rights reserved.
+ * Written by Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ */
+
+#ifndef _LINUX_HOTTRACK_H
+#define _LINUX_HOTTRACK_H
+
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/rbtree.h>
+#include <linux/kref.h>
+#include <linux/fs.h>
+
+#define MAP_BITS 8
+#define MAP_SIZE (1 << MAP_BITS)
+
+/* values for hot_freq flags */
+enum {
+ TYPE_INODE = 0,
+ TYPE_RANGE,
+ MAX_TYPES,
+};
+
+/* An item representing an inode and its access frequency */
+struct hot_inode_item {
+ struct kref refs;
+ struct rb_node rb_node; /* rbtree index */
+ struct rcu_head rcu;
+ struct rb_root hot_range_tree; /* tree of ranges */
+ spinlock_t i_lock; /* protect above tree */
+ struct hot_info *hot_root; /* associated hot_info */
+ u64 ino; /* inode number from inode */
+};
+
+/*
+ * An item representing a range inside of
+ * an inode whose frequency is being tracked
+ */
+struct hot_range_item {
+ struct kref refs;
+ struct rb_node rb_node; /* rbtree index */
+ struct rcu_head rcu;
+ struct hot_inode_item *hot_inode; /* associated hot_inode_item */
+ loff_t start; /* offset in bytes */
+ size_t len; /* length in bytes */
+};
+
+struct hot_info {
+ struct rb_root hot_inode_tree;
+ spinlock_t t_lock; /* protect above tree */
+};
+
+extern int hot_track_init(struct super_block *sb);
+extern void hot_track_exit(struct super_block *sb);
+
+#endif /* _LINUX_HOTTRACK_H */
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 6c28b61..d105d8d 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -86,6 +86,7 @@ struct inodes_stat_t {
#define MS_KERNMOUNT (1<<22) /* this is a kern_mount call */
#define MS_I_VERSION (1<<23) /* Update inode I_version field */
#define MS_STRICTATIME (1<<24) /* Always perform atime updates */
+#define MS_HOTTRACK (1<<25) /* Enable VFS hot tracking */

/* These sb flags are internal to the kernel */
#define MS_NOSEC (1<<28)
--
1.7.11.7