On Sun, Sep 23, 2012 at 08:56:26PM +0800, zwu.kernel@gmail.com wrote:

From: Zhi Yong Wu <redacted>

  One root structure hot_info is defined, is hooked
up in super_block, and will be used to hold rb trees
root, hash list root and some other information, etc.
  Adds hot_inode_tree struct to keep track of
frequently accessed files, and be keyed by {inode, offset}.
Trees contain hot_inode_items representing those files
and ranges.
  Having these trees means that vfs can quickly determine the
temperature of some data by doing some calculations on the
hot_freq_data struct that hangs off of the tree item.
  Define two items hot_inode_item and hot_range_item,
one of them represents one tracked file
to keep track of its access frequency and the tree of
ranges in this file, while the latter represents
a file range of one inode.
  Each of the two structures contains a hot_freq_data
struct with its frequency of access metrics (number of
{reads, writes}, last {read,write} time, frequency of
{reads,writes}).
  Also, each hot_inode_item contains one hot_range_tree
struct which is keyed by {inode, offset, length}
and used to keep track of all the ranges in this file.

Signed-off-by: Zhi Yong Wu <redacted>
---
+

..snip..

+/* A tree that sits on the hot_info */
+struct hot_inode_tree {
+	struct rb_root map;
+	rwlock_t lock;
+};
+
+/* A tree of ranges for each inode in the hot_inode_tree */
+struct hot_range_tree {
+	struct rb_root map;
+	rwlock_t lock;
+};

Can as well have a generic datastructure called hot_tree instead
of having two different datastructure which basically are the same.

+
+/* A frequency data struct holds values that are used to
+ * determine temperature of files and file ranges. These structs
+ * are members of hot_inode_item and hot_range_item
+ */
+struct hot_freq_data {
+	struct timespec last_read_time;
+	struct timespec last_write_time;
+	u32 nr_reads;
+	u32 nr_writes;
+	u64 avg_delta_reads;
+	u64 avg_delta_writes;
+	u8 flags;
+	u32 last_temperature;
+};
+
+/* An item representing an inode and its access frequency */
+struct hot_inode_item {
+	/* node for hot_inode_tree rb_tree */
+	struct rb_node rb_node;
+	/* tree of ranges in this inode */
+	struct hot_range_tree hot_range_tree;
+	/* frequency data for this inode */
+	struct hot_freq_data hot_freq_data;
+	/* inode number, copied from inode */
+	unsigned long i_ino;
+	/* used to check for errors in ref counting */
+	u8 in_tree;
+	/* protects hot_freq_data, i_no, in_tree */
+	spinlock_t lock;
+	/* prevents kfree */
+	struct kref refs;
+};
+
+/*
+ * An item representing a range inside of an inode whose frequency
+ * is being tracked
+ */
+struct hot_range_item {
+	/* node for hot_range_tree rb_tree */
+	struct rb_node rb_node;
+	/* frequency data for this range */
+	struct hot_freq_data hot_freq_data;
+	/* the hot_inode_item associated with this hot_range_item */
+	struct hot_inode_item *hot_inode;
+	/* starting offset of this range */
+	u64 start;
+	/* length of this range */
+	u64 len;
+	/* used to check for errors in ref counting */
+	u8 in_tree;
+	/* protects hot_freq_data, start, len, and in_tree */
+	spinlock_t lock;
+	/* prevents kfree */
+	struct kref refs;
+};

might as well have just one generic datastructure called hot_item with 
all the common fields and then have 

	struct hot_inode_item  {
		struct hot_item hot_inode;
		struct hot_tree hot_range_tree;
		unsigned long i_ino;
	}

	and 

	struct hot_range_item {
		struct hot_item hot_range;
		u64 start;
		u64 len;	/* length of this range */
	}

This should help you eliminate some duplicate code as well.


RP