[RFC v4 00/15] vfs: hot data tracking

[RFC v4 00/15] vfs: hot data tracking

[zwu.kernel]

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

NOTE:

  The patchset can be obtained via my kernel dev git on github:
git@github.com:wuzhy/kernel.git hot_tracking
  If you're interested, you can also can review them via
https://github.com/wuzhy/kernel/commits/hot_tracking

  For more infomation, please check hot_tracking.txt in Documentation

TODO List:

 1.) Need to do scalability or performance tests.
 2.) How to save the file temperature among the umount to be able to
     preserve the file tempreture after reboot

Ben Chociej, Matt Lupfer and Conor Scott originally wrote this code to
 be very btrfs-specific.  I've taken their code and attempted to
make it more generic and integrate it at the VFS level.

Changelog from v3:
 1.) Rewritten debugfs support based seq_file operation. [Dave Chinner]
 2.) Refactored workqueue support. [Dave Chinner]
 3.) Turn some Micro into be tunable        [Zhiyong, Liu Zheng]
       TIME_TO_KICK, and HEAT_UPDATE_DELAY
 4.) Cleanedup a lot of other issues [Dave Chinner]

v2:
 1.) Converted to Radix trees, not RB-tree [Zhiyong, Dave Chinner]
 2.) Added memory shrinker [Dave Chinner]
 3.) Converted to one workqueue to update map info periodically [Dave Chinner]
 4.) Cleanedup a lot of other issues [Dave Chinner]

v1:
 1.) Reduce new files and put all in fs/hot_tracking.[ch] [Dave Chinner]
 2.) The first three patches can probably just be flattened into one.
                                        [Marco Stornelli , Dave Chinner]

Dave Chinner (1):
  xfs: add hot tracking support

Zhi Yong Wu (14):
  vfs,hot_track: introduce private radix tree structures
  vfs,hot_track: initialize and free key data structures
  vfs,hot_track: add the function for collecting I/O frequency
  vfs,hot_track: add two map arrays
  vfs,hot_track: add hooks to enable hot data tracking
  vfs,hot_track: add the function for updating map arrays
  vfs,hot_track: add the aging function
  vfs,hot_track: add one work queue
  vfs,hot_track: register one memory shrinker
  vfs,hot_track: add one new ioctl interface
  vfs,hot_track: add debugfs support
  vfs,hot_track: turn some Micro into be tunable
  btrfs: add hot tracking support
  vfs,hot_track: add the documentation

 Documentation/filesystems/00-INDEX         |    2 +
 Documentation/filesystems/hot_tracking.txt |  164 ++++
 fs/Makefile                                |    2 +-
 fs/btrfs/ctree.h                           |    1 +
 fs/btrfs/super.c                           |   22 +-
 fs/compat_ioctl.c                          |    5 +
 fs/dcache.c                                |    2 +
 fs/debugfs/inode.c                         |   26 +
 fs/direct-io.c                             |    6 +
 fs/hot_tracking.c                          | 1308 ++++++++++++++++++++++++++++
 fs/hot_tracking.h                          |   91 ++
 fs/ioctl.c                                 |   76 ++
 fs/xfs/xfs_mount.h                         |    1 +
 fs/xfs/xfs_super.c                         |   16 +
 include/linux/debugfs.h                    |    9 +
 include/linux/fs.h                         |    4 +
 include/linux/hot_tracking.h               |  125 +++
 kernel/sysctl.c                            |   14 +
 mm/filemap.c                               |    6 +
 mm/page-writeback.c                        |   12 +
 mm/readahead.c                             |    6 +
 21 files changed, 1896 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/filesystems/hot_tracking.txt
 create mode 100644 fs/hot_tracking.c
 create mode 100644 fs/hot_tracking.h
 create mode 100644 include/linux/hot_tracking.h

-- 
1.7.6.5

[RFC v4 01/15] vfs,hot_track: introduce private radix tree structures

[zwu.kernel]

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

  One root structure hot_info is defined, is hooked
up in super_block, and will be used to hold radix tree
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 <wuzhy@linux.vnet.ibm.com>
---
 fs/Makefile                  |    2 +-
 fs/dcache.c                  |    2 +
 fs/hot_tracking.c            |  107 ++++++++++++++++++++++++++++++++++++++++++
 fs/hot_tracking.h            |   23 +++++++++
 include/linux/hot_tracking.h |   73 ++++++++++++++++++++++++++++
 5 files changed, 206 insertions(+), 1 deletions(-)
 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 1d7af79..f966dea 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 drop_caches.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 3a463d0..7d5be16 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -37,6 +37,7 @@
 #include <linux/rculist_bl.h>
 #include <linux/prefetch.h>
 #include <linux/ratelimit.h>
+#include <linux/hot_tracking.h>
 #include "internal.h"
 #include "mount.h"
 
@@ -3172,4 +3173,5 @@ 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..6a0f2a3
--- /dev/null
+++ b/fs/hot_tracking.c
@@ -0,0 +1,107 @@
+/*
+ * fs/hot_tracking.c
+ *
+ * Copyright (C) 2012 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/slab.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/hardirq.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/types.h>
+#include <linux/limits.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;
+
+/*
+ * Initialize the inode tree. Should be called for each new inode
+ * access or other user of the hot_inode interface.
+ */
+static void hot_inode_tree_init(struct hot_info *root)
+{
+	INIT_RADIX_TREE(&root->hot_inode_tree, GFP_ATOMIC);
+	spin_lock_init(&root->lock);
+}
+
+/*
+ * Initialize the hot range tree. Should be called for each new inode
+ * access or other user of the hot_range interface.
+ */
+void hot_range_tree_init(struct hot_inode_item *he)
+{
+	INIT_RADIX_TREE(&he->hot_range_tree, GFP_ATOMIC);
+	spin_lock_init(&he->lock);
+}
+
+/*
+ * Initialize a new hot_range_item structure. The new structure is
+ * returned with a reference count of one and needs to be
+ * freed using free_range_item()
+ */
+static void hot_range_item_init(struct hot_range_item *hr, u32 start,
+				struct hot_inode_item *he)
+{
+	hr->start = start;
+	hr->len = RANGE_SIZE;
+	hr->hot_inode = he;
+	kref_init(&hr->hot_range.refs);
+	spin_lock_init(&hr->hot_range.lock);
+	hr->hot_range.hot_freq_data.avg_delta_reads = (u64) -1;
+	hr->hot_range.hot_freq_data.avg_delta_writes = (u64) -1;
+	hr->hot_range.hot_freq_data.flags = FREQ_DATA_TYPE_RANGE;
+}
+
+/*
+ * Initialize a new hot_inode_item structure. The new structure is
+ * returned with a reference count of one and needs to be
+ * freed using hot_free_inode_item()
+ */
+static void hot_inode_item_init(struct hot_inode_item *he, u64 ino,
+				struct radix_tree_root *hot_inode_tree)
+{
+	he->i_ino = ino;
+	he->hot_inode_tree = hot_inode_tree;
+	kref_init(&he->hot_inode.refs);
+	spin_lock_init(&he->hot_inode.lock);
+	he->hot_inode.hot_freq_data.avg_delta_reads = (u64) -1;
+	he->hot_inode.hot_freq_data.avg_delta_writes = (u64) -1;
+	he->hot_inode.hot_freq_data.flags = FREQ_DATA_TYPE_INODE;
+	hot_range_tree_init(he);
+}
+
+/*
+ * Initialize kmem cache for hot_inode_item and hot_range_item.
+ */
+void __init hot_cache_init(void)
+{
+	hot_inode_item_cachep = kmem_cache_create("hot_inode_item",
+			sizeof(struct hot_inode_item), 0,
+			SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
+			NULL);
+	if (!hot_inode_item_cachep)
+		return;
+
+	hot_range_item_cachep = kmem_cache_create("hot_range_item",
+			sizeof(struct hot_range_item), 0,
+			SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
+			NULL);
+	if (!hot_range_item_cachep)
+		goto err;
+
+	return;
+
+err:
+	kmem_cache_destroy(hot_inode_item_cachep);
+}
diff --git a/fs/hot_tracking.h b/fs/hot_tracking.h
new file mode 100644
index 0000000..febf699
--- /dev/null
+++ b/fs/hot_tracking.h
@@ -0,0 +1,23 @@
+/*
+ * fs/hot_tracking.h
+ *
+ * Copyright (C) 2012 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/radix-tree.h>
+#include <linux/workqueue.h>
+#include <linux/hot_tracking.h>
+
+/* values for hot_freq_data flags */
+#define FREQ_DATA_TYPE_INODE (1 << 0)
+#define FREQ_DATA_TYPE_RANGE (1 << 1)
+
+#endif /* __HOT_TRACKING__ */
diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
new file mode 100644
index 0000000..fcd4ad1
--- /dev/null
+++ b/include/linux/hot_tracking.h
@@ -0,0 +1,73 @@
+/*
+ *  include/linux/hot_tracking.h
+ *
+ * This file has definitions for VFS hot data tracking
+ * structures etc.
+ *
+ * Copyright (C) 2012 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/rbtree.h>
+#include <linux/kref.h>
+#include <linux/fs.h>
+
+/*
+ * 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;
+	u32 flags;
+	u32 last_temp;
+};
+
+/* The common info for both following structures */
+struct hot_comm_item {
+	struct hot_freq_data hot_freq_data;  /* frequency data */
+	spinlock_t lock; /* protects object data */
+	struct kref refs;  /* prevents kfree */
+};
+
+/* An item representing an inode and its access frequency */
+struct hot_inode_item {
+	struct hot_comm_item hot_inode; /* node in hot_inode_tree */
+	struct radix_tree_root hot_range_tree; /* tree of ranges */
+	spinlock_t lock; /* protect range tree */
+	struct radix_tree_root *hot_inode_tree;
+	u64 i_ino; /* inode number from inode */
+};
+
+/*
+ * An item representing a range inside of
+ * an inode whose frequency is being tracked
+ */
+struct hot_range_item {
+	struct hot_comm_item hot_range;
+	struct hot_inode_item *hot_inode; /* associated hot_inode_item */
+	u32 start; /* item index in hot_range_tree */
+	u32 len; /* length in bytes */
+};
+
+struct hot_info {
+	struct radix_tree_root hot_inode_tree;
+	spinlock_t lock; /*protect inode tree */
+};
+
+void __init hot_cache_init(void);
+
+#endif  /* _LINUX_HOTTRACK_H */
-- 
1.7.6.5

[RFC v4 02/15] vfs,hot_track: initialize and free key data structures

[zwu.kernel]

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

  Add initialization function to create some
key data structures when hot tracking is enabled;
Clean up them when hot tracking is disabled

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/hot_tracking.c            |  125 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h           |    4 +
 include/linux/hot_tracking.h |    3 +
 3 files changed, 132 insertions(+), 0 deletions(-)

diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
index 6a0f2a3..5fef7e5 100644
--- a/fs/hot_tracking.c
+++ b/fs/hot_tracking.c
@@ -21,6 +21,8 @@
 #include <linux/limits.h>
 #include "hot_tracking.h"
 
+static struct hot_info *hot_root;
+
 /* 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;
@@ -75,12 +77,102 @@ static void hot_inode_item_init(struct hot_inode_item *he, u64 ino,
 	he->hot_inode_tree = hot_inode_tree;
 	kref_init(&he->hot_inode.refs);
 	spin_lock_init(&he->hot_inode.lock);
+	INIT_LIST_HEAD(&he->hot_inode.n_list);
 	he->hot_inode.hot_freq_data.avg_delta_reads = (u64) -1;
 	he->hot_inode.hot_freq_data.avg_delta_writes = (u64) -1;
 	he->hot_inode.hot_freq_data.flags = FREQ_DATA_TYPE_INODE;
 	hot_range_tree_init(he);
 }
 
+static void hot_range_item_free(struct kref *kref)
+{
+	struct hot_comm_item *comm_item = container_of(kref,
+		struct hot_comm_item, refs);
+	struct hot_range_item *hr = container_of(comm_item,
+		struct hot_range_item, hot_range);
+
+	radix_tree_delete(&hr->hot_inode->hot_range_tree, hr->start);
+	kmem_cache_free(hot_range_item_cachep, hr);
+}
+
+/*
+ * 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->hot_range.refs, hot_range_item_free);
+}
+
+/* Frees the entire hot_range_tree. */
+static void hot_range_tree_free(struct hot_inode_item *he)
+{
+	struct hot_range_item *hr_nodes[8];
+	u32 start = 0;
+	int i, n;
+
+	while (1) {
+		spin_lock(&he->lock);
+		n = radix_tree_gang_lookup(&he->hot_range_tree,
+					(void **)hr_nodes, start,
+					ARRAY_SIZE(hr_nodes));
+		if (!n) {
+			spin_unlock(&he->lock);
+			break;
+		}
+
+		start = hr_nodes[n - 1]->start + 1;
+		for (i = 0; i < n; i++)
+			hot_range_item_put(hr_nodes[i]);
+		spin_unlock(&he->lock);
+	}
+}
+
+static void hot_inode_item_free(struct kref *kref)
+{
+	struct hot_comm_item *comm_item = container_of(kref,
+			struct hot_comm_item, refs);
+	struct hot_inode_item *he = container_of(comm_item,
+			struct hot_inode_item, hot_inode);
+
+	hot_range_tree_free(he);
+	radix_tree_delete(he->hot_inode_tree, he->i_ino);
+	kmem_cache_free(hot_inode_item_cachep, he);
+}
+
+/*
+ * 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->hot_inode.refs, hot_inode_item_free);
+}
+
+/* Frees the entire hot_inode_tree. */
+static void hot_inode_tree_exit(struct hot_info *root)
+{
+	struct hot_inode_item *hi_nodes[8];
+	u64 ino = 0;
+	int i, n;
+
+	while (1) {
+		spin_lock(&root->lock);
+		n = radix_tree_gang_lookup(&root->hot_inode_tree,
+					   (void **)hi_nodes, ino,
+					   ARRAY_SIZE(hi_nodes));
+		if (!n) {
+			spin_unlock(&root->lock);
+			break;
+		}
+
+		ino = hi_nodes[n - 1]->i_ino + 1;
+		for (i = 0; i < n; i++)
+			hot_inode_item_put(hi_nodes[i]);
+		spin_unlock(&root->lock);
+	}
+}
+
 /*
  * Initialize kmem cache for hot_inode_item and hot_range_item.
  */
@@ -105,3 +197,36 @@ void __init hot_cache_init(void)
 err:
 	kmem_cache_destroy(hot_inode_item_cachep);
 }
+
+/*
+ * Initialize the data structures for hot data tracking.
+ */
+int hot_track_init(struct super_block *sb)
+{
+	struct hot_info *root;
+	int ret = -ENOMEM;
+
+	root = kzalloc(sizeof(struct hot_info), GFP_NOFS);
+	if (!root) {
+		printk(KERN_ERR "%s: Failed to malloc memory for "
+				"hot_info\n", __func__);
+		return ret;
+	}
+
+	sb->s_hot_root = hot_root = root;
+	hot_inode_tree_init(root);
+
+	printk(KERN_INFO "VFS: Turning on hot data tracking\n");
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hot_track_init);
+
+void hot_track_exit(struct super_block *sb)
+{
+	struct hot_info *root = sb->s_hot_root;
+
+	hot_inode_tree_exit(root);
+	kfree(root);
+}
+EXPORT_SYMBOL_GPL(hot_track_exit);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b33cfc9..c541ae7 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -27,6 +27,7 @@
 #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>
@@ -1321,6 +1322,9 @@ struct super_block {
 
 	/* Being remounted read-only */
 	int s_readonly_remount;
+
+	/* Hot data tracking*/
+	struct hot_info *s_hot_root;
 };
 
 /* superblock cache pruning functions */
diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
index fcd4ad1..592a6eb 100644
--- a/include/linux/hot_tracking.h
+++ b/include/linux/hot_tracking.h
@@ -69,5 +69,8 @@ struct hot_info {
 };
 
 void __init hot_cache_init(void);
+int hot_track_init(struct super_block *sb);
+void hot_track_exit(struct super_block *sb);
+
 
 #endif  /* _LINUX_HOTTRACK_H */
-- 
1.7.6.5

[RFC v4 03/15] vfs,hot_track: add the function for collecting I/O frequency

[zwu.kernel]

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

  Add some utils helpers to update access frequencies
for one file or its range.

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/hot_tracking.c            |  191 ++++++++++++++++++++++++++++++++++++++++++
 fs/hot_tracking.h            |    9 ++
 include/linux/hot_tracking.h |    2 +
 3 files changed, 202 insertions(+), 0 deletions(-)

diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
index 5fef7e5..201598b 100644
--- a/fs/hot_tracking.c
+++ b/fs/hot_tracking.c
@@ -173,6 +173,149 @@ static void hot_inode_tree_exit(struct hot_info *root)
 	}
 }
 
+struct hot_inode_item
+*hot_inode_item_find(struct hot_info *root, u64 ino)
+{
+	struct hot_inode_item *he;
+	int ret;
+
+again:
+	spin_lock(&root->lock);
+	he = radix_tree_lookup(&root->hot_inode_tree, ino);
+	if (he) {
+		kref_get(&he->hot_inode.refs);
+		spin_unlock(&root->lock);
+		return he;
+	}
+	spin_unlock(&root->lock);
+
+	he = kmem_cache_zalloc(hot_inode_item_cachep,
+				GFP_KERNEL | GFP_NOFS);
+	if (!he)
+		return ERR_PTR(-ENOMEM);
+
+	hot_inode_item_init(he, ino, &root->hot_inode_tree);
+
+	ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
+	if (ret) {
+		kmem_cache_free(hot_inode_item_cachep, he);
+		return ERR_PTR(ret);
+	}
+
+	spin_lock(&root->lock);
+	ret = radix_tree_insert(&root->hot_inode_tree, ino, he);
+	if (ret == -EEXIST) {
+		kmem_cache_free(hot_inode_item_cachep, he);
+		spin_unlock(&root->lock);
+		radix_tree_preload_end();
+		goto again;
+	}
+	spin_unlock(&root->lock);
+	radix_tree_preload_end();
+
+	kref_get(&he->hot_inode.refs);
+	return he;
+}
+
+static struct hot_range_item
+*hot_range_item_find(struct hot_inode_item *he,
+			u32 start)
+{
+	struct hot_range_item *hr;
+	int ret;
+
+again:
+	spin_lock(&he->lock);
+	hr = radix_tree_lookup(&he->hot_range_tree, start);
+	if (hr) {
+		kref_get(&hr->hot_range.refs);
+		spin_unlock(&he->lock);
+		return hr;
+	}
+	spin_unlock(&he->lock);
+
+	hr = kmem_cache_zalloc(hot_range_item_cachep,
+				GFP_KERNEL | GFP_NOFS);
+	if (!hr)
+		return ERR_PTR(-ENOMEM);
+
+	hot_range_item_init(hr, start, he);
+
+	ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
+	if (ret) {
+		kmem_cache_free(hot_range_item_cachep, hr);
+		return ERR_PTR(ret);
+	}
+
+	spin_lock(&he->lock);
+	ret = radix_tree_insert(&he->hot_range_tree, start, hr);
+	if (ret == -EEXIST) {
+		kmem_cache_free(hot_range_item_cachep, hr);
+		spin_unlock(&he->lock);
+		radix_tree_preload_end();
+		goto again;
+	}
+	spin_unlock(&he->lock);
+	radix_tree_preload_end();
+
+	kref_get(&hr->hot_range.refs);
+	return hr;
+}
+
+/*
+ * This function does the actual work of updating the frequency numbers,
+ * whatever they turn out to be. FREQ_POWER determines how many atime
+ * deltas we keep track of (as a power of 2). So, setting it to anything above
+ * 16ish is probably overkill. Also, the higher the power, the more bits get
+ * right shifted out of the timestamp, reducing precision, so take note of that
+ * as well.
+ *
+ * The caller should have already locked freq_data's parent's spinlock.
+ *
+ * FREQ_POWER, defined immediately below, determines how heavily to weight
+ * the current frequency numbers against the newest access. For example, a value
+ * of 4 means that the new access information will be weighted 1/16th (ie 2^-4)
+ * as heavily as the existing frequency info. In essence, this is a kludged-
+ * together version of a weighted average, since we can't afford to keep all of
+ * the information that it would take to get a _real_ weighted average.
+ */
+static u64 hot_average_update(struct timespec old_atime,
+		struct timespec cur_time, u64 old_avg)
+{
+	struct timespec delta_ts;
+	u64 new_avg;
+	u64 new_delta;
+
+	delta_ts = timespec_sub(cur_time, old_atime);
+	new_delta = timespec_to_ns(&delta_ts) >> FREQ_POWER;
+
+	new_avg = (old_avg << FREQ_POWER) - old_avg + new_delta;
+	new_avg = new_avg >> FREQ_POWER;
+
+	return new_avg;
+}
+
+static void hot_freq_data_update(struct hot_freq_data *freq_data, bool write)
+{
+	struct timespec cur_time = current_kernel_time();
+
+	if (write) {
+		freq_data->nr_writes += 1;
+		freq_data->avg_delta_writes = hot_average_update(
+				freq_data->last_write_time,
+				cur_time,
+				freq_data->avg_delta_writes);
+		freq_data->last_write_time = cur_time;
+	} else {
+		freq_data->nr_reads += 1;
+		freq_data->avg_delta_reads = hot_average_update(
+				freq_data->last_read_time,
+				cur_time,
+				freq_data->avg_delta_reads);
+		freq_data->last_read_time = cur_time;
+	}
+}
+
 /*
  * Initialize kmem cache for hot_inode_item and hot_range_item.
  */
@@ -199,6 +342,54 @@ err:
 }
 
 /*
+ * Main function to update access frequency from read/writepage(s) hooks
+ */
+inline void hot_update_freqs(struct inode *inode, u64 start,
+			u64 len, int rw)
+{
+	struct hot_info *root = inode->i_sb->s_hot_root;
+	struct hot_inode_item *he;
+	struct hot_range_item *hr;
+	u32 cur, end;
+
+	if (!root || (len == 0))
+		return;
+
+	he = hot_inode_item_find(root, inode->i_ino);
+	if (IS_ERR(he)) {
+		WARN_ON(1);
+		return;
+	}
+
+	spin_lock(&he->hot_inode.lock);
+	hot_freq_data_update(&he->hot_inode.hot_freq_data, rw);
+	spin_unlock(&he->hot_inode.lock);
+
+	/*
+	 * Align ranges on RANGE_SIZE boundary
+	 * to prevent proliferation of range structs
+	 */
+	end = (start + len + RANGE_SIZE - 1) >> RANGE_BITS;
+	for (cur = (start >> RANGE_BITS); cur < end; cur++) {
+		hr = hot_range_item_find(he, cur);
+		if (IS_ERR(hr)) {
+			WARN_ON(1);
+			hot_inode_item_put(he);
+			return;
+		}
+
+		spin_lock(&hr->hot_range.lock);
+		hot_freq_data_update(&hr->hot_range.hot_freq_data, rw);
+		spin_unlock(&hr->hot_range.lock);
+
+		hot_range_item_put(hr);
+	}
+
+	hot_inode_item_put(he);
+}
+EXPORT_SYMBOL_GPL(hot_update_freqs);
+
+/*
  * Initialize the data structures for hot data tracking.
  */
 int hot_track_init(struct super_block *sb)
diff --git a/fs/hot_tracking.h b/fs/hot_tracking.h
index febf699..3e5f5d0 100644
--- a/fs/hot_tracking.h
+++ b/fs/hot_tracking.h
@@ -19,5 +19,14 @@
 /* values for hot_freq_data flags */
 #define FREQ_DATA_TYPE_INODE (1 << 0)
 #define FREQ_DATA_TYPE_RANGE (1 << 1)
+/* size of sub-file ranges */
+#define RANGE_BITS 20
+#define RANGE_SIZE (1 << RANGE_BITS)
+
+#define FREQ_POWER 4
+
+struct hot_inode_item
+*hot_inode_item_find(struct hot_info *root, u64 ino);
+void hot_inode_item_put(struct hot_inode_item *he);
 
 #endif /* __HOT_TRACKING__ */
diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
index 592a6eb..de68f66 100644
--- a/include/linux/hot_tracking.h
+++ b/include/linux/hot_tracking.h
@@ -72,5 +72,7 @@ void __init hot_cache_init(void);
 int hot_track_init(struct super_block *sb);
 void hot_track_exit(struct super_block *sb);
 
+inline void hot_update_freqs(struct inode *inode, u64 start,
+				u64 len, int rw);
 
 #endif  /* _LINUX_HOTTRACK_H */
-- 
1.7.6.5

[RFC v4 04/15] vfs,hot_track: add two map arrays

[zwu.kernel]

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

  Adds two map arrays which contains
a lot of list and is used to efficiently
look up the data temperature of a file or its
ranges.
  In each list of map arrays, the array node
will keep track of temperature info.

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/hot_tracking.c            |   55 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/hot_tracking.h |   16 ++++++++++++
 2 files changed, 71 insertions(+), 0 deletions(-)

diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
index 201598b..b5568bc 100644
--- a/fs/hot_tracking.c
+++ b/fs/hot_tracking.c
@@ -60,6 +60,7 @@ static void hot_range_item_init(struct hot_range_item *hr, u32 start,
 	hr->hot_inode = he;
 	kref_init(&hr->hot_range.refs);
 	spin_lock_init(&hr->hot_range.lock);
+	INIT_LIST_HEAD(&hr->hot_range.n_list);
 	hr->hot_range.hot_freq_data.avg_delta_reads = (u64) -1;
 	hr->hot_range.hot_freq_data.avg_delta_writes = (u64) -1;
 	hr->hot_range.hot_freq_data.flags = FREQ_DATA_TYPE_RANGE;
@@ -91,6 +92,13 @@ static void hot_range_item_free(struct kref *kref)
 	struct hot_range_item *hr = container_of(comm_item,
 		struct hot_range_item, hot_range);
 
+	spin_lock(&hr->hot_range.lock);
+	if (!list_empty(&hr->hot_range.n_list)) {
+		list_del_init(&hr->hot_range.n_list);
+		hot_root->hot_map_nr--;
+	}
+	spin_unlock(&hr->hot_range.lock);
+
 	radix_tree_delete(&hr->hot_inode->hot_range_tree, hr->start);
 	kmem_cache_free(hot_range_item_cachep, hr);
 }
@@ -135,6 +143,13 @@ static void hot_inode_item_free(struct kref *kref)
 	struct hot_inode_item *he = container_of(comm_item,
 			struct hot_inode_item, hot_inode);
 
+	spin_lock(&he->hot_inode.lock);
+	if (!list_empty(&he->hot_inode.n_list)) {
+		list_del_init(&he->hot_inode.n_list);
+		hot_root->hot_map_nr--;
+	}
+	spin_unlock(&he->hot_inode.lock);
+
 	hot_range_tree_free(he);
 	radix_tree_delete(he->hot_inode_tree, he->i_ino);
 	kmem_cache_free(hot_inode_item_cachep, he);
@@ -317,6 +332,44 @@ static void hot_freq_data_update(struct hot_freq_data *freq_data, bool write)
 }
 
 /*
+ * Initialize inode and range map arrays.
+ */
+static void hot_map_array_init(struct hot_info *root)
+{
+	int i;
+	for (i = 0; i < HEAT_MAP_SIZE; i++) {
+		INIT_LIST_HEAD(&root->heat_inode_map[i].node_list);
+		INIT_LIST_HEAD(&root->heat_range_map[i].node_list);
+		root->heat_inode_map[i].temp = i;
+		root->heat_range_map[i].temp = i;
+	}
+}
+
+static void hot_map_list_free(struct list_head *node_list,
+				struct hot_info *root)
+{
+	struct list_head *pos, *next;
+	struct hot_comm_item *node;
+
+	list_for_each_safe(pos, next, node_list) {
+		node = list_entry(pos, struct hot_comm_item, n_list);
+		list_del_init(&node->n_list);
+		root->hot_map_nr--;
+	}
+
+}
+
+/* Free inode and range map arrays */
+static void hot_map_array_exit(struct hot_info *root)
+{
+	int i;
+	for (i = 0; i < HEAT_MAP_SIZE; i++) {
+		hot_map_list_free(&root->heat_inode_map[i].node_list, root);
+		hot_map_list_free(&root->heat_range_map[i].node_list, root);
+	}
+}
+
+/*
  * Initialize kmem cache for hot_inode_item and hot_range_item.
  */
 void __init hot_cache_init(void)
@@ -406,6 +459,7 @@ int hot_track_init(struct super_block *sb)
 
 	sb->s_hot_root = hot_root = root;
 	hot_inode_tree_init(root);
+	hot_map_array_init(root);
 
 	printk(KERN_INFO "VFS: Turning on hot data tracking\n");
 
@@ -417,6 +471,7 @@ void hot_track_exit(struct super_block *sb)
 {
 	struct hot_info *root = sb->s_hot_root;
 
+	hot_map_array_exit(root);
 	hot_inode_tree_exit(root);
 	kfree(root);
 }
diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
index de68f66..0ce2ef8 100644
--- a/include/linux/hot_tracking.h
+++ b/include/linux/hot_tracking.h
@@ -20,6 +20,9 @@
 #include <linux/kref.h>
 #include <linux/fs.h>
 
+#define HEAT_MAP_BITS 8
+#define HEAT_MAP_SIZE (1 << HEAT_MAP_BITS)
+
 /*
  * A frequency data struct holds values that are used to
  * determine temperature of files and file ranges. These structs
@@ -36,11 +39,18 @@ struct hot_freq_data {
 	u32 last_temp;
 };
 
+/* List heads in hot map array */
+struct hot_map_head {
+	struct list_head node_list;
+	u8 temp;
+};
+
 /* The common info for both following structures */
 struct hot_comm_item {
 	struct hot_freq_data hot_freq_data;  /* frequency data */
 	spinlock_t lock; /* protects object data */
 	struct kref refs;  /* prevents kfree */
+	struct list_head n_list; /* list node index */
 };
 
 /* An item representing an inode and its access frequency */
@@ -66,6 +76,12 @@ struct hot_range_item {
 struct hot_info {
 	struct radix_tree_root hot_inode_tree;
 	spinlock_t lock; /*protect inode tree */
+
+	/* map of inode temperature */
+	struct hot_map_head heat_inode_map[HEAT_MAP_SIZE];
+	/* map of range temperature */
+	struct hot_map_head heat_range_map[HEAT_MAP_SIZE];
+	unsigned int hot_map_nr;
 };
 
 void __init hot_cache_init(void);
-- 
1.7.6.5

[RFC v4 05/15] vfs,hot_track: add hooks to enable hot data tracking

[zwu.kernel]

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

  Miscellaneous features that implement hot data tracking
and generally make the hot data functions a bit more friendly.

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/direct-io.c      |    6 ++++++
 mm/filemap.c        |    6 ++++++
 mm/page-writeback.c |   12 ++++++++++++
 mm/readahead.c      |    6 ++++++
 4 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/fs/direct-io.c b/fs/direct-io.c
index f86c720..1d23631 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -37,6 +37,7 @@
 #include <linux/uio.h>
 #include <linux/atomic.h>
 #include <linux/prefetch.h>
+#include "hot_tracking.h"
 
 /*
  * How many user pages to map in one call to get_user_pages().  This determines
@@ -1297,6 +1298,11 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
 	prefetch(bdev->bd_queue);
 	prefetch((char *)bdev->bd_queue + SMP_CACHE_BYTES);
 
+	/* Hot data tracking */
+	hot_update_freqs(inode, (u64)offset,
+			(u64)iov_length(iov, nr_segs),
+			rw & WRITE);
+
 	return do_blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
 				     nr_segs, get_block, end_io,
 				     submit_io, flags);
diff --git a/mm/filemap.c b/mm/filemap.c
index 83efee7..51b2c48 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -33,6 +33,7 @@
 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
 #include <linux/memcontrol.h>
 #include <linux/cleancache.h>
+#include <linux/hot_tracking.h>
 #include "internal.h"
 
 /*
@@ -1224,6 +1225,11 @@ readpage:
 		 * PG_error will be set again if readpage fails.
 		 */
 		ClearPageError(page);
+
+		/* Hot data tracking */
+		hot_update_freqs(inode, (u64)page->index << PAGE_CACHE_SHIFT,
+				PAGE_CACHE_SIZE, 0);
+
 		/* Start the actual read. The read will unlock the page. */
 		error = mapping->a_ops->readpage(filp, page);
 
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 830893b..5220040 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -35,6 +35,7 @@
 #include <linux/buffer_head.h> /* __set_page_dirty_buffers */
 #include <linux/pagevec.h>
 #include <linux/timer.h>
+#include <linux/hot_tracking.h>
 #include <trace/events/writeback.h>
 
 /*
@@ -1903,13 +1904,24 @@ EXPORT_SYMBOL(generic_writepages);
 int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
 {
 	int ret;
+	pgoff_t start = 0;
+	u64 count = 0;
 
 	if (wbc->nr_to_write <= 0)
 		return 0;
+
+	start = mapping->writeback_index << PAGE_CACHE_SHIFT;
+	count = (u64)wbc->nr_to_write;
+
 	if (mapping->a_ops->writepages)
 		ret = mapping->a_ops->writepages(mapping, wbc);
 	else
 		ret = generic_writepages(mapping, wbc);
+
+	/* Hot data tracking */
+	hot_update_freqs(mapping->host, (u64)start,
+			(count - (u64)wbc->nr_to_write) * PAGE_CACHE_SIZE, 1);
+
 	return ret;
 }
 
diff --git a/mm/readahead.c b/mm/readahead.c
index 7963f23..8a24f1e 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -19,6 +19,7 @@
 #include <linux/pagemap.h>
 #include <linux/syscalls.h>
 #include <linux/file.h>
+#include <linux/hot_tracking.h>
 
 /*
  * Initialise a struct file's readahead state.  Assumes that the caller has
@@ -138,6 +139,11 @@ static int read_pages(struct address_space *mapping, struct file *filp,
 out:
 	blk_finish_plug(&plug);
 
+	/* Hot data tracking */
+	hot_update_freqs(mapping->host, (u64)(list_entry(pages->prev,\
+				struct page, lru)->index) << PAGE_CACHE_SHIFT,
+			(u64)nr_pages * PAGE_CACHE_SIZE, 0);
+
 	return ret;
 }
 
-- 
1.7.6.5

[RFC v4 06/15] vfs,hot_track: add the function for updating map arrays

[zwu.kernel]

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

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/hot_tracking.c |  164 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/hot_tracking.h |   54 +++++++++++++++++
 2 files changed, 218 insertions(+), 0 deletions(-)

diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
index b5568bc..05624ad 100644
--- a/fs/hot_tracking.c
+++ b/fs/hot_tracking.c
@@ -331,6 +331,170 @@ static void hot_freq_data_update(struct hot_freq_data *freq_data, bool write)
 	}
 }
 
+static u64 hot_raw_shift(u64 counter, u32 bits, bool dir)
+{
+	if (dir)
+		return counter << bits;
+	else
+		return counter >> bits;
+}
+
+/*
+ * hot_temp_calc() is responsible for distilling the six heat
+ * criteria, which are described in detail in hot_tracking.h) down into a single
+ * temperature value for the data, which is an integer between 0
+ * and HEAT_MAX_VALUE.
+ *
+ * To accomplish this, the raw values from the hot_freq_data structure
+ * are shifted various ways in order to make the temperature calculation more
+ * or less sensitive to each value.
+ *
+ * Once this calibration has happened, we do some additional normalization and
+ * make sure that everything fits nicely in a u32. From there, we take a very
+ * rudimentary kind of "average" of each of the values, where the *_COEFF_POWER
+ * values act as weights for the average.
+ *
+ * Finally, we use the HEAT_HASH_BITS value, which determines the size of the
+ * heat list array, to normalize the temperature to the proper granularity.
+ */
+u32 hot_temp_calc(struct hot_freq_data *freq_data)
+{
+	u32 result = 0;
+
+	struct timespec ckt = current_kernel_time();
+	u64 cur_time = timespec_to_ns(&ckt);
+
+	u32 nrr_heat = (u32)hot_raw_shift((u64)freq_data->nr_reads,
+					NRR_MULTIPLIER_POWER, true);
+	u32 nrw_heat = (u32)hot_raw_shift((u64)freq_data->nr_writes,
+					NRW_MULTIPLIER_POWER, true);
+
+	u64 ltr_heat =
+	hot_raw_shift((cur_time - timespec_to_ns(&freq_data->last_read_time)),
+			LTR_DIVIDER_POWER, false);
+	u64 ltw_heat =
+	hot_raw_shift((cur_time - timespec_to_ns(&freq_data->last_write_time)),
+			LTW_DIVIDER_POWER, false);
+
+	u64 avr_heat =
+	hot_raw_shift((((u64) -1) - freq_data->avg_delta_reads),
+			AVR_DIVIDER_POWER, false);
+	u64 avw_heat =
+	hot_raw_shift((((u64) -1) - freq_data->avg_delta_writes),
+			AVW_DIVIDER_POWER, false);
+
+	/* ltr_heat is now guaranteed to be u32 safe */
+	if (ltr_heat >= hot_raw_shift((u64) 1, 32, true))
+		ltr_heat = 0;
+	else
+		ltr_heat = hot_raw_shift((u64) 1, 32, true) - ltr_heat;
+
+	/* ltw_heat is now guaranteed to be u32 safe */
+	if (ltw_heat >= hot_raw_shift((u64) 1, 32, true))
+		ltw_heat = 0;
+	else
+		ltw_heat = hot_raw_shift((u64) 1, 32, true) - ltw_heat;
+
+	/* avr_heat is now guaranteed to be u32 safe */
+	if (avr_heat >= hot_raw_shift((u64) 1, 32, true))
+		avr_heat = (u32) -1;
+
+	/* avw_heat is now guaranteed to be u32 safe */
+	if (avw_heat >= hot_raw_shift((u64) 1, 32, true))
+		avw_heat = (u32) -1;
+
+	nrr_heat = (u32)hot_raw_shift((u64)nrr_heat,
+		(3 - NRR_COEFF_POWER), false);
+	nrw_heat = (u32)hot_raw_shift((u64)nrw_heat,
+		(3 - NRW_COEFF_POWER), false);
+	ltr_heat = hot_raw_shift(ltr_heat, (3 - LTR_COEFF_POWER), false);
+	ltw_heat = hot_raw_shift(ltw_heat, (3 - LTW_COEFF_POWER), false);
+	avr_heat = hot_raw_shift(avr_heat, (3 - AVR_COEFF_POWER), false);
+	avw_heat = hot_raw_shift(avw_heat, (3 - AVW_COEFF_POWER), false);
+
+	result = nrr_heat + nrw_heat + (u32) ltr_heat +
+		(u32) ltw_heat + (u32) avr_heat + (u32) avw_heat;
+
+	return result;
+}
+
+/*
+ * Calculate a new temperature and, if necessary,
+ * move the list_head corresponding to this inode or range
+ * to the proper list with the new temperature
+ */
+static void hot_map_array_update(struct hot_freq_data *freq_data,
+				struct hot_info *root)
+{
+	struct hot_map_head *buckets, *cur_bucket;
+	struct hot_comm_item *comm_item;
+	struct hot_inode_item *he;
+	struct hot_range_item *hr;
+	u8 a_temp, b_temp;
+	u32 temp = 0;
+
+	comm_item = container_of(freq_data,
+			struct hot_comm_item, hot_freq_data);
+
+	if (freq_data->flags & FREQ_DATA_TYPE_INODE) {
+		he = container_of(comm_item,
+			struct hot_inode_item, hot_inode);
+		buckets = root->heat_inode_map;
+
+		spin_lock(&he->hot_inode.lock);
+		temp = hot_temp_calc(freq_data);
+		spin_unlock(&he->hot_inode.lock);
+
+		if (he == NULL)
+			return;
+
+		spin_lock(&he->hot_inode.lock);
+		a_temp = temp >> (32 - HEAT_MAP_BITS);
+		b_temp = freq_data->last_temp >> (32 - HEAT_MAP_BITS);
+		if (list_empty(&he->hot_inode.n_list) || (a_temp != b_temp)) {
+			if (!list_empty(&he->hot_inode.n_list)) {
+				list_del_init(&he->hot_inode.n_list);
+				root->hot_map_nr--;
+			}
+
+			cur_bucket = buckets + a_temp;
+			list_add_tail(&he->hot_inode.n_list,
+					&cur_bucket->node_list);
+			root->hot_map_nr++;
+			freq_data->last_temp = temp;
+		}
+		spin_unlock(&he->hot_inode.lock);
+	} else if (freq_data->flags & FREQ_DATA_TYPE_RANGE) {
+		hr = container_of(comm_item,
+			struct hot_range_item, hot_range);
+		buckets = root->heat_range_map;
+
+		spin_lock(&hr->hot_range.lock);
+		temp = hot_temp_calc(freq_data);
+		spin_unlock(&hr->hot_range.lock);
+
+		if (hr == NULL)
+			return;
+
+		spin_lock(&hr->hot_range.lock);
+		a_temp = temp >> (32 - HEAT_MAP_BITS);
+		b_temp = freq_data->last_temp >> (32 - HEAT_MAP_BITS);
+		if (list_empty(&hr->hot_range.n_list) || (a_temp != b_temp)) {
+			if (!list_empty(&hr->hot_range.n_list)) {
+				list_del_init(&hr->hot_range.n_list);
+				root->hot_map_nr--;
+			}
+
+			cur_bucket = buckets + a_temp;
+			list_add_tail(&hr->hot_range.n_list,
+					&cur_bucket->node_list);
+			root->hot_map_nr++;
+			freq_data->last_temp = temp;
+		}
+		spin_unlock(&hr->hot_range.lock);
+	}
+}
+
 /*
  * Initialize inode and range map arrays.
  */
diff --git a/fs/hot_tracking.h b/fs/hot_tracking.h
index 3e5f5d0..be2365c 100644
--- a/fs/hot_tracking.h
+++ b/fs/hot_tracking.h
@@ -25,8 +25,62 @@
 
 #define FREQ_POWER 4
 
+/*
+ * The following comments explain what exactly comprises a unit of heat.
+ *
+ * Each of six values of heat are calculated and combined in order to form an
+ * overall temperature for the data:
+ *
+ * NRR - number of reads since mount
+ * NRW - number of writes since mount
+ * LTR - time elapsed since last read (ns)
+ * LTW - time elapsed since last write (ns)
+ * AVR - average delta between recent reads (ns)
+ * AVW - average delta between recent writes (ns)
+ *
+ * These values are divided (right-shifted) according to the *_DIVIDER_POWER
+ * values defined below to bring the numbers into a reasonable range. You can
+ * modify these values to fit your needs. However, each heat unit is a u32 and
+ * thus maxes out at 2^32 - 1. Therefore, you must choose your dividers quite
+ * carefully or else they could max out or be stuck at zero quite easily.
+ *
+ * (E.g., if you chose AVR_DIVIDER_POWER = 0, nothing less than 4s of atime
+ * delta would bring the temperature above zero, ever.)
+ *
+ * Finally, each value is added to the overall temperature between 0 and 8
+ * times, depending on its *_COEFF_POWER value. Note that the coefficients are
+ * also actually implemented with shifts, so take care to treat these values
+ * as powers of 2. (I.e., 0 means we'll add it to the temp once; 1 = 2x, etc.)
+ */
+
+/* NRR/NRW heat unit = 2^X accesses */
+#define NRR_MULTIPLIER_POWER 20
+#define NRR_COEFF_POWER 0
+#define NRW_MULTIPLIER_POWER 20
+#define NRW_COEFF_POWER 0
+
+/* LTR/LTW heat unit = 2^X ns of age */
+#define LTR_DIVIDER_POWER 30
+#define LTR_COEFF_POWER 1
+#define LTW_DIVIDER_POWER 30
+#define LTW_COEFF_POWER 1
+
+/*
+ * AVR/AVW cold unit = 2^X ns of average delta
+ * AVR/AVW heat unit = HEAT_MAX_VALUE - cold unit
+ *
+ * E.g., data with an average delta between 0 and 2^X ns
+ * will have a cold value of 0, which means a heat value
+ * equal to HEAT_MAX_VALUE.
+ */
+#define AVR_DIVIDER_POWER 40
+#define AVR_COEFF_POWER 0
+#define AVW_DIVIDER_POWER 40
+#define AVW_COEFF_POWER 0
+
 struct hot_inode_item
 *hot_inode_item_find(struct hot_info *root, u64 ino);
 void hot_inode_item_put(struct hot_inode_item *he);
+u32 hot_temp_calc(struct hot_freq_data *freq_data);
 
 #endif /* __HOT_TRACKING__ */
-- 
1.7.6.5

[RFC v4 07/15] vfs,hot_track: add the aging function

[zwu.kernel]

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

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/hot_tracking.c |   56 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/hot_tracking.h |    6 +++++
 2 files changed, 62 insertions(+), 0 deletions(-)

diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
index 05624ad..575cd3a 100644
--- a/fs/hot_tracking.c
+++ b/fs/hot_tracking.c
@@ -331,6 +331,24 @@ static void hot_freq_data_update(struct hot_freq_data *freq_data, bool write)
 	}
 }
 
+static bool hot_freq_data_is_obsolete(struct hot_freq_data *freq_data)
+{
+	int ret = 0;
+	struct timespec ckt = current_kernel_time();
+
+	u64 cur_time = timespec_to_ns(&ckt);
+	u64 last_read_ns =
+		(cur_time - timespec_to_ns(&freq_data->last_read_time));
+	u64 last_write_ns =
+		(cur_time - timespec_to_ns(&freq_data->last_write_time));
+	u64 kick_ns =  TIME_TO_KICK * NSEC_PER_SEC;
+
+	if ((last_read_ns > kick_ns) && (last_write_ns > kick_ns))
+		ret = 1;
+
+	return ret;
+}
+
 static u64 hot_raw_shift(u64 counter, u32 bits, bool dir)
 {
 	if (dir)
@@ -495,6 +513,44 @@ static void hot_map_array_update(struct hot_freq_data *freq_data,
 	}
 }
 
+/* Update temperatures for each range item for aging purposes */
+static void hot_range_update(struct hot_inode_item *he,
+					struct hot_info *root)
+{
+	struct hot_range_item *hr_nodes[8];
+	u32 start = 0;
+	bool obsolete;
+	int i, n;
+
+	while (1) {
+		spin_lock(&he->lock);
+		n = radix_tree_gang_lookup(&he->hot_range_tree,
+				(void **)hr_nodes, start,
+				ARRAY_SIZE(hr_nodes));
+		if (!n) {
+			spin_unlock(&he->lock);
+			break;
+		}
+		spin_unlock(&he->lock);
+
+		start = hr_nodes[n - 1]->start + 1;
+		for (i = 0; i < n; i++) {
+			kref_get(&hr_nodes[i]->hot_range.refs);
+			hot_map_array_update(
+				&hr_nodes[i]->hot_range.hot_freq_data, root);
+
+			spin_lock(&hr_nodes[i]->hot_range.lock);
+			obsolete = hot_freq_data_is_obsolete(
+					&hr_nodes[i]->hot_range.hot_freq_data);
+			spin_unlock(&hr_nodes[i]->hot_range.lock);
+
+			hot_range_item_put(hr_nodes[i]);
+			if (obsolete)
+				hot_range_item_put(hr_nodes[i]);
+		}
+	}
+}
+
 /*
  * Initialize inode and range map arrays.
  */
diff --git a/fs/hot_tracking.h b/fs/hot_tracking.h
index be2365c..67c6fb6 100644
--- a/fs/hot_tracking.h
+++ b/fs/hot_tracking.h
@@ -26,6 +26,12 @@
 #define FREQ_POWER 4
 
 /*
+ * time to quit keeping track of
+ * tracking data (seconds)
+ */
+#define TIME_TO_KICK 300
+
+/*
  * The following comments explain what exactly comprises a unit of heat.
  *
  * Each of six values of heat are calculated and combined in order to form an
-- 
1.7.6.5

[RFC v4 08/15] vfs,hot_track: add one work queue

[zwu.kernel]

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

  Add a per-superblock workqueue and a work_struct
to run periodic work to update map info on each superblock.

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/hot_tracking.c            |   85 ++++++++++++++++++++++++++++++++++++++++++
 fs/hot_tracking.h            |    3 +
 include/linux/hot_tracking.h |    3 +
 3 files changed, 91 insertions(+), 0 deletions(-)

diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
index 575cd3a..d931083 100644
--- a/fs/hot_tracking.c
+++ b/fs/hot_tracking.c
@@ -15,9 +15,12 @@
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <linux/hardirq.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
 #include <linux/fs.h>
 #include <linux/blkdev.h>
 #include <linux/types.h>
+#include <linux/list_sort.h>
 #include <linux/limits.h>
 #include "hot_tracking.h"
 
@@ -589,6 +592,67 @@ static void hot_map_array_exit(struct hot_info *root)
 	}
 }
 
+/* Temperature compare function*/
+static int hot_temp_cmp(void *priv, struct list_head *a,
+				struct list_head *b)
+{
+	struct hot_comm_item *ap =
+			container_of(a, struct hot_comm_item, n_list);
+	struct hot_comm_item *bp =
+			container_of(b, struct hot_comm_item, n_list);
+
+	int diff = ap->hot_freq_data.last_temp
+				- bp->hot_freq_data.last_temp;
+	if (diff > 0)
+		return -1;
+	if (diff < 0)
+		return 1;
+	return 0;
+}
+
+/*
+ * Every sync period we update temperatures for
+ * each hot inode item and hot range item for aging
+ * purposes.
+ */
+static void hot_update_worker(struct work_struct *work)
+{
+	struct hot_info *root = container_of(to_delayed_work(work),
+					struct hot_info, update_work);
+	struct hot_inode_item *hi_nodes[8];
+	u64 ino = 0;
+	int i, n;
+
+	while (1) {
+		n = radix_tree_gang_lookup(&root->hot_inode_tree,
+				   (void **)hi_nodes, ino,
+				   ARRAY_SIZE(hi_nodes));
+		if (!n)
+			break;
+
+		ino = hi_nodes[n - 1]->i_ino + 1;
+		for (i = 0; i < n; i++) {
+			kref_get(&hi_nodes[i]->hot_inode.refs);
+			hot_map_array_update(
+				&hi_nodes[i]->hot_inode.hot_freq_data, root);
+			hot_range_update(hi_nodes[i], root);
+			hot_inode_item_put(hi_nodes[i]);
+		}
+	}
+
+	/* Sort temperature map info */
+	for (i = 0; i < HEAT_MAP_SIZE; i++) {
+		list_sort(NULL, &root->heat_inode_map[i].node_list,
+			hot_temp_cmp);
+		list_sort(NULL, &root->heat_range_map[i].node_list,
+			hot_temp_cmp);
+	}
+
+	/* Instert next delayed work */
+	queue_delayed_work(root->update_wq, &root->update_work,
+		msecs_to_jiffies(HEAT_UPDATE_DELAY * MSEC_PER_SEC));
+}
+
 /*
  * Initialize kmem cache for hot_inode_item and hot_range_item.
  */
@@ -681,9 +745,28 @@ int hot_track_init(struct super_block *sb)
 	hot_inode_tree_init(root);
 	hot_map_array_init(root);
 
+	root->update_wq = alloc_workqueue(
+		"hot_update_wq", WQ_NON_REENTRANT, 0);
+	if (!root->update_wq) {
+		printk(KERN_ERR "%s: Failed to create "
+				"hot update workqueue\n", __func__);
+		goto failed_wq;
+	}
+
+	/* Initialize hot tracking wq and arm one delayed work */
+	INIT_DELAYED_WORK(&root->update_work, hot_update_worker);
+	queue_delayed_work(root->update_wq, &root->update_work,
+		msecs_to_jiffies(HEAT_UPDATE_DELAY * MSEC_PER_SEC));
+
 	printk(KERN_INFO "VFS: Turning on hot data tracking\n");
 
 	return 0;
+
+failed_wq:
+	hot_map_array_exit(root);
+	hot_inode_tree_exit(root);
+	kfree(root);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(hot_track_init);
 
@@ -691,6 +774,8 @@ void hot_track_exit(struct super_block *sb)
 {
 	struct hot_info *root = sb->s_hot_root;
 
+	cancel_delayed_work_sync(&root->update_work);
+	destroy_workqueue(root->update_wq);
 	hot_map_array_exit(root);
 	hot_inode_tree_exit(root);
 	kfree(root);
diff --git a/fs/hot_tracking.h b/fs/hot_tracking.h
index 67c6fb6..b9d9717 100644
--- a/fs/hot_tracking.h
+++ b/fs/hot_tracking.h
@@ -31,6 +31,9 @@
  */
 #define TIME_TO_KICK 300
 
+/* set how often to update temperatures (seconds) */
+#define HEAT_UPDATE_DELAY 300
+
 /*
  * The following comments explain what exactly comprises a unit of heat.
  *
diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
index 0ce2ef8..4c5f5f3 100644
--- a/include/linux/hot_tracking.h
+++ b/include/linux/hot_tracking.h
@@ -82,6 +82,9 @@ struct hot_info {
 	/* map of range temperature */
 	struct hot_map_head heat_range_map[HEAT_MAP_SIZE];
 	unsigned int hot_map_nr;
+
+	struct workqueue_struct *update_wq;
+	struct delayed_work update_work;
 };
 
 void __init hot_cache_init(void);
-- 
1.7.6.5

[RFC v4 09/15] vfs,hot_track: register one memory shrinker

[zwu.kernel]

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

  Register a shrinker to control the amount of
memory that is used in tracking hot regions - if we are throwing
inodes out of memory due to memory pressure, we most definitely are
going to need to reduce the amount of memory the tracking code is
using, even if it means losing useful information (i.e. the shrinker
accelerates the aging process).

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/hot_tracking.c            |   61 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/hot_tracking.h |    1 +
 2 files changed, 62 insertions(+), 0 deletions(-)

diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
index d931083..7d2c53d 100644
--- a/fs/hot_tracking.c
+++ b/fs/hot_tracking.c
@@ -678,6 +678,61 @@ err:
 	kmem_cache_destroy(hot_inode_item_cachep);
 }
 
+static int hot_track_prune_map(struct hot_map_head *map_head,
+				bool type, int nr)
+{
+	struct hot_comm_item *node;
+	int i;
+
+	for (i = 0; i < HEAT_MAP_SIZE; i++) {
+		while (!list_empty(&(map_head + i)->node_list)) {
+			if (nr-- <= 0)
+				break;
+
+			node = list_first_entry(&(map_head + i)->node_list,
+					struct hot_comm_item, n_list);
+			if (type) {
+				struct hot_inode_item *hot_inode =
+					container_of(node,
+					struct hot_inode_item, hot_inode);
+				hot_inode_item_put(hot_inode);
+			} else {
+				struct hot_range_item *hot_range =
+					container_of(node,
+					struct hot_range_item, hot_range);
+				hot_range_item_put(hot_range);
+			}
+		}
+	}
+
+	return nr;
+}
+
+/* The shrinker callback function */
+static int hot_track_prune(struct shrinker *shrink,
+			struct shrink_control *sc)
+{
+	struct hot_info *root =
+		container_of(shrink, struct hot_info, hot_shrink);
+	int ret;
+
+	if (sc->nr_to_scan == 0)
+		return root->hot_map_nr;
+
+	if (!(sc->gfp_mask & __GFP_FS))
+		return -1;
+
+	ret = hot_track_prune_map(root->heat_range_map,
+				false, sc->nr_to_scan);
+	if (ret > 0)
+		ret = hot_track_prune_map(root->heat_inode_map,
+					true, ret);
+	if (ret > 0)
+		root->hot_map_nr -= (sc->nr_to_scan - ret);
+
+	return root->hot_map_nr;
+}
+
 /*
  * Main function to update access frequency from read/writepage(s) hooks
  */
@@ -758,6 +813,11 @@ int hot_track_init(struct super_block *sb)
 	queue_delayed_work(root->update_wq, &root->update_work,
 		msecs_to_jiffies(HEAT_UPDATE_DELAY * MSEC_PER_SEC));
 
+	/* Register a shrinker callback */
+	root->hot_shrink.shrink = hot_track_prune;
+	root->hot_shrink.seeks = DEFAULT_SEEKS;
+	register_shrinker(&root->hot_shrink);
+
 	printk(KERN_INFO "VFS: Turning on hot data tracking\n");
 
 	return 0;
@@ -774,6 +834,7 @@ void hot_track_exit(struct super_block *sb)
 {
 	struct hot_info *root = sb->s_hot_root;
 
+	unregister_shrinker(&root->hot_shrink);
 	cancel_delayed_work_sync(&root->update_work);
 	destroy_workqueue(root->update_wq);
 	hot_map_array_exit(root);
diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
index 4c5f5f3..446c99e 100644
--- a/include/linux/hot_tracking.h
+++ b/include/linux/hot_tracking.h
@@ -85,6 +85,7 @@ struct hot_info {
 
 	struct workqueue_struct *update_wq;
 	struct delayed_work update_work;
+	struct shrinker hot_shrink;
 };
 
 void __init hot_cache_init(void);
-- 
1.7.6.5

[RFC v4 10/15] vfs,hot_track: add one new ioctl interface

[zwu.kernel]

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

  FS_IOC_GET_HEAT_INFO: return a struct containing the various
metrics collected in hot_freq_data structs, and also return a
calculated data temperature based on those metrics. Optionally, retrieve
the temperature from the hot data hash list instead of recalculating it.

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/compat_ioctl.c            |    5 +++
 fs/ioctl.c                   |   76 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/hot_tracking.h |   19 ++++++++++
 3 files changed, 100 insertions(+), 0 deletions(-)

diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c
index f505402..b346324 100644
--- a/fs/compat_ioctl.c
+++ b/fs/compat_ioctl.c
@@ -57,6 +57,7 @@
 #include <linux/i2c-dev.h>
 #include <linux/atalk.h>
 #include <linux/gfp.h>
+#include <linux/hot_tracking.h>
 
 #include <net/bluetooth/bluetooth.h>
 #include <net/bluetooth/hci.h>
@@ -1398,6 +1399,9 @@ COMPATIBLE_IOCTL(TIOCSTART)
 COMPATIBLE_IOCTL(TIOCSTOP)
 #endif
 
+/*Hot data tracking*/
+COMPATIBLE_IOCTL(FS_IOC_GET_HEAT_INFO)
+
 /* fat 'r' ioctls. These are handled by fat with ->compat_ioctl,
    but we don't want warnings on other file systems. So declare
    them as compatible here. */
@@ -1577,6 +1581,7 @@ asmlinkage long compat_sys_ioctl(unsigned int fd, unsigned int cmd,
 	case FIBMAP:
 	case FIGETBSZ:
 	case FIONREAD:
+	case FS_IOC_GET_HEAT_INFO:
 		if (S_ISREG(f.file->f_path.dentry->d_inode->i_mode))
 			break;
 		/*FALL THROUGH*/
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 3bdad6d..fbad2be 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -15,6 +15,7 @@
 #include <linux/writeback.h>
 #include <linux/buffer_head.h>
 #include <linux/falloc.h>
+#include "hot_tracking.h"
 
 #include <asm/ioctls.h>
 
@@ -537,6 +538,78 @@ static int ioctl_fsthaw(struct file *filp)
 }
 
 /*
+ * Retrieve information about access frequency for the given file. Return it in
+ * a userspace-friendly struct for btrfsctl (or another tool) to parse.
+ *
+ * The temperature that is returned can be "live" -- that is, recalculated when
+ * the ioctl is called -- or it can be returned from the hashtable, reflecting
+ * the (possibly old) value that the system will use when considering files
+ * for migration. This behavior is determined by hot_heat_info->live.
+ */
+static int ioctl_heat_info(struct file *file, void __user *argp)
+{
+	struct inode *inode = file->f_dentry->d_inode;
+	struct hot_heat_info *heat_info;
+	struct hot_inode_item *he;
+	int ret = 0;
+
+	heat_info = kmalloc(sizeof(struct hot_heat_info),
+				GFP_KERNEL | GFP_NOFS);
+
+	if (copy_from_user((void *) heat_info,
+			argp,
+			sizeof(struct hot_heat_info)) != 0) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+	he = hot_inode_item_find(inode->i_sb->s_hot_root, inode->i_ino);
+	if (!he) {
+		/* we don't have any info on this file yet */
+		ret = -ENODATA;
+		goto err;
+	}
+
+	spin_lock(&he->hot_inode.lock);
+	heat_info->avg_delta_reads =
+		(__u64) he->hot_inode.hot_freq_data.avg_delta_reads;
+	heat_info->avg_delta_writes =
+		(__u64) he->hot_inode.hot_freq_data.avg_delta_writes;
+	heat_info->last_read_time =
+	(__u64) timespec_to_ns(&he->hot_inode.hot_freq_data.last_read_time);
+	heat_info->last_write_time =
+	(__u64) timespec_to_ns(&he->hot_inode.hot_freq_data.last_write_time);
+	heat_info->num_reads =
+		(__u32) he->hot_inode.hot_freq_data.nr_reads;
+	heat_info->num_writes =
+		(__u32) he->hot_inode.hot_freq_data.nr_writes;
+
+	if (heat_info->live > 0) {
+		/*
+		 * got a request for live temperature,
+		 * call hot_hash_calc_temperature to recalculate
+		 */
+		heat_info->temp = hot_temp_calc(&he->hot_inode.hot_freq_data);
+	} else {
+		/* not live temperature, get it from the hashlist */
+		heat_info->temp = he->hot_inode.hot_freq_data.last_temp;
+	}
+	spin_unlock(&he->hot_inode.lock);
+
+	hot_inode_item_put(he);
+
+	if (copy_to_user(argp, (void *) heat_info,
+			sizeof(struct hot_heat_info))) {
+		ret = -EFAULT;
+		goto err;
+	}
+
+err:
+	kfree(heat_info);
+	return ret;
+}
+
+/*
  * When you add any new common ioctls to the switches above and below
  * please update compat_sys_ioctl() too.
  *
@@ -591,6 +664,9 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
 	case FIGETBSZ:
 		return put_user(inode->i_sb->s_blocksize, argp);
 
+	case FS_IOC_GET_HEAT_INFO:
+		return ioctl_heat_info(filp, argp);
+
 	default:
 		if (S_ISREG(inode->i_mode))
 			error = file_ioctl(filp, cmd, arg);
diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
index 446c99e..c81c331 100644
--- a/include/linux/hot_tracking.h
+++ b/include/linux/hot_tracking.h
@@ -39,6 +39,17 @@ struct hot_freq_data {
 	u32 last_temp;
 };
 
+struct hot_heat_info {
+	__u64 avg_delta_reads;
+	__u64 avg_delta_writes;
+	__u64 last_read_time;
+	__u64 last_write_time;
+	__u32 num_reads;
+	__u32 num_writes;
+	__u32 temp;
+	__u8 live;
+};
+
 /* List heads in hot map array */
 struct hot_map_head {
 	struct list_head node_list;
@@ -88,6 +99,14 @@ struct hot_info {
 	struct shrinker hot_shrink;
 };
 
+/*
+ * Hot data tracking ioctls:
+ *
+ * HOT_INFO - retrieve info on frequency of access
+ */
+#define FS_IOC_GET_HEAT_INFO _IOR('f', 17, \
+			struct hot_heat_info)
+
 void __init hot_cache_init(void);
 int hot_track_init(struct super_block *sb);
 void hot_track_exit(struct super_block *sb);
-- 
1.7.6.5

[RFC v4 11/15] vfs,hot_track: add debugfs support

[zwu.kernel]

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

  Add a /sys/kernel/debug/hot_track/<device_name>/ directory for each
volume that contains two files. The first, `inode_stats', contains the
heat information for inodes that have been brought into the hot data map
structures. The second, `range_stats', contains similar information for
subfile ranges.

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/debugfs/inode.c           |   26 +++
 fs/hot_tracking.c            |  458 ++++++++++++++++++++++++++++++++++++++++++
 fs/hot_tracking.h            |    5 +
 include/linux/debugfs.h      |    9 +
 include/linux/hot_tracking.h |    1 +
 5 files changed, 499 insertions(+), 0 deletions(-)

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index b607d92..c6291bc 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -354,6 +354,32 @@ exit:
 	return dentry;
 }
 
+struct dentry *debugfs_get_dentry(const char *name,
+			struct dentry *parent, int len)
+{
+	struct dentry *dentry = NULL;
+	int error = 0;
+
+	error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
+				&debugfs_mount_count);
+	if (error)
+		return NULL;
+
+	if (!parent)
+		parent = debugfs_mount->mnt_root;
+
+	mutex_lock(&parent->d_inode->i_mutex);
+	dentry = lookup_one_len(name, parent, strlen(name));
+	if (!IS_ERR(dentry)) {
+		mutex_unlock(&parent->d_inode->i_mutex);
+		return dentry;
+	}
+	mutex_unlock(&parent->d_inode->i_mutex);
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(debugfs_get_dentry);
+
 /**
  * debugfs_create_file - create a file in the debugfs filesystem
  * @name: a pointer to a string containing the name of the file to create.
diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
index 7d2c53d..18a64ee 100644
--- a/fs/hot_tracking.c
+++ b/fs/hot_tracking.c
@@ -21,6 +21,7 @@
 #include <linux/blkdev.h>
 #include <linux/types.h>
 #include <linux/list_sort.h>
+#include <linux/debugfs.h>
 #include <linux/limits.h>
 #include "hot_tracking.h"
 
@@ -654,6 +655,451 @@ static void hot_update_worker(struct work_struct *work)
 }
 
 /*
+ * take the inode, find ranges associated with inode
+ * and print each range data struct
+ */
+static struct hot_range_item
+*hot_range_tree_walk(struct hot_inode_item *he,
+			loff_t *pos, u32 start, bool flag)
+{
+	struct hot_range_item *hr_nodes[8];
+	loff_t l = *pos;
+	int i, n;
+
+	/* Walk the hot_range_tree for inode */
+	while (1) {
+		spin_lock(&he->lock);
+		n = radix_tree_gang_lookup(&he->hot_range_tree,
+					   (void **)hr_nodes, start,
+					   ARRAY_SIZE(hr_nodes));
+		if (!n) {
+			spin_unlock(&he->lock);
+			break;
+		}
+		spin_unlock(&he->lock);
+
+		start = hr_nodes[n - 1]->start + 1;
+		for (i = 0; i < n; i++) {
+			if ((!flag && !l--) || (flag)) {
+				if (flag)
+					(*pos)++;
+				kref_get(&hr_nodes[i]->hot_range.refs);
+				return hr_nodes[i];
+			}
+		}
+	}
+
+	return NULL;
+}
+
+static void
+*hot_inode_tree_walk(u64 ino, loff_t *pos, bool type, bool flag)
+{
+	struct hot_inode_item *hi_nodes[8];
+	struct hot_range_item *hr;
+	loff_t l = *pos;
+	int i, n;
+
+	while (1) {
+		spin_lock(&hot_root->lock);
+		n = radix_tree_gang_lookup(&hot_root->hot_inode_tree,
+					(void **)hi_nodes, ino,
+					ARRAY_SIZE(hi_nodes));
+		if (!n) {
+			spin_unlock(&hot_root->lock);
+			break;
+		}
+		spin_unlock(&hot_root->lock);
+
+		ino = hi_nodes[n - 1]->i_ino + 1;
+		for (i = 0; i < n; i++) {
+			if (!type) {
+				hr = hot_range_tree_walk(hi_nodes[i],
+						pos, 0, flag);
+				if (hr)
+					return hr;
+			} else {
+				if ((!flag && !l--) || (flag)) {
+					if (flag)
+						(*pos)++;
+					kref_get(&hi_nodes[i]->hot_inode.refs);
+					return hi_nodes[i];
+				}
+			}
+		}
+	}
+
+	return NULL;
+}
+
+static void *hot_range_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	return hot_inode_tree_walk(0, pos, false, false);
+}
+
+static void *hot_range_seq_next(struct seq_file *seq,
+				void *v, loff_t *pos)
+{
+	struct hot_range_item *hr_next, *hr = v;
+	u32 start = hr->start + 1;
+
+	/* Walk the hot_range_tree for inode */
+	hr_next = hot_range_tree_walk(hr->hot_inode, pos, start, true);
+	if (hr_next)
+		return hr_next;
+
+	return hot_inode_tree_walk(hr->hot_inode->i_ino + 1,
+				pos, false, true);
+}
+
+static void hot_range_seq_stop(struct seq_file *seq, void *v)
+{
+	struct hot_range_item *hr = v;
+
+	if (hr)
+		hot_range_item_put(hr);
+}
+
+static int hot_range_seq_show(struct seq_file *seq, void *v)
+{
+	struct hot_range_item *hr = v;
+	struct hot_inode_item *he = hr->hot_inode;
+	struct hot_freq_data *freq_data = &hr->hot_range.hot_freq_data;
+
+	/* Always lock hot_inode_item first */
+	spin_lock(&he->hot_inode.lock);
+	spin_lock(&hr->hot_range.lock);
+	seq_printf(seq, "inode #%llu, range start " \
+			"%llu (range len %u) reads %u, writes %u, "
+			"avg read time %llu, avg write time %llu, temp %u\n",
+			he->i_ino,
+			(u64)hr->start * RANGE_SIZE,
+			hr->len,
+			freq_data->nr_reads,
+			freq_data->nr_writes,
+			freq_data->avg_delta_reads / NSEC_PER_MSEC,
+			freq_data->avg_delta_writes / NSEC_PER_MSEC,
+			freq_data->last_temp >> (32 - HEAT_MAP_BITS));
+	spin_unlock(&hr->hot_range.lock);
+	spin_unlock(&he->hot_inode.lock);
+
+	return 0;
+}
+
+static void *hot_inode_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	return hot_inode_tree_walk(0, pos, true, false);
+}
+
+static void *hot_inode_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct hot_inode_item *he = v;
+	u64 ino = he->i_ino + 1;
+
+	hot_inode_item_put(he);
+
+	return hot_inode_tree_walk(ino, pos, true, true);
+}
+
+static void hot_inode_seq_stop(struct seq_file *seq, void *v)
+{
+	struct hot_inode_item *he = v;
+
+	if (he)
+		hot_inode_item_put(he);
+}
+
+static int hot_inode_seq_show(struct seq_file *seq, void *v)
+{
+	struct hot_inode_item *he = v;
+	struct hot_freq_data *freq_data = &he->hot_inode.hot_freq_data;
+
+	spin_lock(&he->hot_inode.lock);
+	seq_printf(seq, "inode #%llu, reads %u, writes %u, " \
+		"avg read time %llu, avg write time %llu, temp %u\n",
+		he->i_ino,
+		freq_data->nr_reads,
+		freq_data->nr_writes,
+		freq_data->avg_delta_reads / NSEC_PER_MSEC,
+		freq_data->avg_delta_writes / NSEC_PER_MSEC,
+		freq_data->last_temp >> (32 - HEAT_MAP_BITS));
+	spin_unlock(&he->hot_inode.lock);
+
+	return 0;
+}
+
+static void *hot_spot_range_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	struct hot_range_item *hr;
+	struct hot_comm_item *comm_item;
+	struct list_head *n_list;
+	int i;
+
+	for (i = HEAT_MAP_SIZE - 1; i >= 0; i--) {
+		n_list = seq_list_start(
+			&hot_root->heat_range_map[i].node_list, *pos);
+		if (n_list) {
+			comm_item = container_of(n_list,
+				struct hot_comm_item, n_list);
+			hr = container_of(comm_item,
+				struct hot_range_item, hot_range);
+			kref_get(&hr->hot_range.refs);
+			return hr;
+		}
+	}
+
+	return NULL;
+}
+
+static void *hot_spot_range_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct hot_range_item *hr_next, *hr = v;
+	struct hot_comm_item *comm_item;
+	struct list_head *n_list;
+	int i =
+	 hr->hot_range.hot_freq_data.last_temp >> (32 - HEAT_MAP_BITS);
+
+	n_list = seq_list_next(&hr->hot_range.n_list,
+		&hot_root->heat_range_map[i].node_list, pos);
+	hot_range_item_put(hr);
+next:
+	if (n_list) {
+		comm_item = container_of(n_list,
+			struct hot_comm_item, n_list);
+		hr_next = container_of(comm_item,
+			struct hot_range_item, hot_range);
+		kref_get(&hr_next->hot_range.refs);
+		return hr_next;
+	} else if (--i >= 0) {
+		n_list = seq_list_next(&hot_root->heat_range_map[i].node_list,
+				&hot_root->heat_range_map[i].node_list, pos);
+		goto next;
+	}
+
+	return NULL;
+}
+
+static void *hot_spot_inode_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	struct hot_inode_item *he;
+	struct hot_comm_item *comm_item;
+	struct list_head *n_list;
+	int i;
+
+	for (i = HEAT_MAP_SIZE - 1; i >= 0; i--) {
+		n_list = seq_list_start(
+			&hot_root->heat_inode_map[i].node_list, *pos);
+		if (n_list) {
+			comm_item = container_of(n_list,
+				struct hot_comm_item, n_list);
+			he = container_of(comm_item,
+				struct hot_inode_item, hot_inode);
+			kref_get(&he->hot_inode.refs);
+			return he;
+		}
+	}
+
+	return NULL;
+}
+
+static void *hot_spot_inode_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct hot_inode_item *he_next, *he = v;
+	struct hot_comm_item *comm_item;
+	struct list_head *n_list;
+	int i =
+	 he->hot_inode.hot_freq_data.last_temp >> (32 - HEAT_MAP_BITS);
+
+	n_list = seq_list_next(&he->hot_inode.n_list,
+			&hot_root->heat_inode_map[i].node_list, pos);
+	hot_inode_item_put(he);
+next:
+	if (n_list) {
+		comm_item = container_of(n_list,
+			struct hot_comm_item, n_list);
+		he_next = container_of(comm_item,
+			struct hot_inode_item, hot_inode);
+		kref_get(&he_next->hot_inode.refs);
+		return he_next;
+	} else if (--i >= 0) {
+		n_list = seq_list_next(&hot_root->heat_inode_map[i].node_list,
+				&hot_root->heat_inode_map[i].node_list, pos);
+		goto next;
+	}
+
+	return NULL;
+}
+
+static const struct seq_operations hot_range_seq_ops = {
+	.start = hot_range_seq_start,
+	.next = hot_range_seq_next,
+	.stop = hot_range_seq_stop,
+	.show = hot_range_seq_show
+};
+
+static const struct seq_operations hot_inode_seq_ops = {
+	.start = hot_inode_seq_start,
+	.next = hot_inode_seq_next,
+	.stop = hot_inode_seq_stop,
+	.show = hot_inode_seq_show
+};
+
+static const struct seq_operations hot_spot_range_seq_ops = {
+	.start = hot_spot_range_seq_start,
+	.next = hot_spot_range_seq_next,
+	.stop = hot_range_seq_stop,
+	.show = hot_range_seq_show
+};
+
+static const struct seq_operations hot_spot_inode_seq_ops = {
+	.start = hot_spot_inode_seq_start,
+	.next = hot_spot_inode_seq_next,
+	.stop = hot_inode_seq_stop,
+	.show = hot_inode_seq_show
+};
+
+static int hot_range_seq_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &hot_range_seq_ops);
+}
+
+static int hot_inode_seq_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &hot_inode_seq_ops);
+}
+
+static int hot_spot_range_seq_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &hot_spot_range_seq_ops);
+}
+
+static int hot_spot_inode_seq_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &hot_spot_inode_seq_ops);
+}
+
+/* fops to override for printing range data */
+static const struct file_operations hot_debugfs_range_fops = {
+	.open = hot_range_seq_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = seq_release,
+};
+
+/* fops to override for printing inode data */
+static const struct file_operations hot_debugfs_inode_fops = {
+	.open = hot_inode_seq_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = seq_release,
+};
+
+/* fops to override for printing temperature data */
+static const struct file_operations hot_debugfs_spot_range_fops = {
+	.open = hot_spot_range_seq_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = seq_release,
+};
+
+static const struct file_operations hot_debugfs_spot_inode_fops = {
+	.open = hot_spot_inode_seq_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = seq_release,
+};
+
+static const struct hot_debugfs hot_debugfs[] = {
+	{
+		.name = "rt_stats_range",
+		.fops  = &hot_debugfs_range_fops,
+	},
+	{
+		.name = "rt_stats_inode",
+		.fops  = &hot_debugfs_inode_fops,
+	},
+	{
+		.name = "hot_spots_range",
+		.fops  = &hot_debugfs_spot_range_fops,
+	},
+	{
+		.name = "hot_spots_inode",
+		.fops  = &hot_debugfs_spot_inode_fops,
+	},
+};
+
+/* initialize debugfs */
+static int hot_debugfs_init(struct super_block *sb)
+{
+	static const char hot_name[] = "hot_track";
+	struct dentry *vol_dentry, *dentry;
+	int i, ret = 0;
+
+	/* Determine if hot debufs root has existed */
+	sb->s_hot_root->debugfs_root =
+			debugfs_get_dentry(hot_name, NULL, strlen(hot_name));
+	if (IS_ERR_OR_NULL(sb->s_hot_root->debugfs_root)
+		|| !sb->s_hot_root->debugfs_root->d_inode) {
+		sb->s_hot_root->debugfs_root =
+			debugfs_create_dir(hot_name, NULL);
+		if (IS_ERR(sb->s_hot_root->debugfs_root)) {
+			ret = PTR_ERR(sb->s_hot_root->debugfs_root);
+			return ret;
+		}
+	}
+
+	if (!S_ISDIR(sb->s_hot_root->debugfs_root->d_inode->i_mode))
+		return -ENOTDIR;
+
+	/* create debugfs folder for this volume by mounted dev name */
+	vol_dentry = debugfs_create_dir(sb->s_id, sb->s_hot_root->debugfs_root);
+	if (IS_ERR(vol_dentry)) {
+		ret = PTR_ERR(vol_dentry);
+		goto err;
+	}
+
+	/* create debugfs hot data files */
+	for (i = 0; i < ARRAY_SIZE(hot_debugfs); i++) {
+		dentry = debugfs_create_file(hot_debugfs[i].name,
+					S_IFREG | S_IRUSR | S_IWUSR,
+					vol_dentry,
+					NULL,
+					hot_debugfs[i].fops);
+		if (IS_ERR(dentry)) {
+			ret = PTR_ERR(dentry);
+			goto err;
+		}
+	}
+
+	return 0;
+
+err:
+	debugfs_remove_recursive(vol_dentry);
+
+	if (list_empty(&sb->s_hot_root->debugfs_root->d_subdirs))
+		debugfs_remove(sb->s_hot_root->debugfs_root);
+
+	return ret;
+}
+
+/* remove dentries for debugsfs */
+static void hot_debugfs_exit(struct super_block *sb)
+{
+	struct dentry *vol_dentry;
+
+	vol_dentry = debugfs_get_dentry(sb->s_id,
+				sb->s_hot_root->debugfs_root, strlen(sb->s_id));
+	/* remove all debugfs entries recursively from the volume root */
+	if (vol_dentry)
+		debugfs_remove_recursive(vol_dentry);
+	else
+		BUG_ON(1);
+
+	if (list_empty(&sb->s_hot_root->debugfs_root->d_subdirs))
+		debugfs_remove(sb->s_hot_root->debugfs_root);
+}
+
+/*
  * Initialize kmem cache for hot_inode_item and hot_range_item.
  */
 void __init hot_cache_init(void)
@@ -818,10 +1264,21 @@ int hot_track_init(struct super_block *sb)
 	root->hot_shrink.seeks = DEFAULT_SEEKS;
 	register_shrinker(&root->hot_shrink);
 
+	ret = hot_debugfs_init(sb);
+	if (ret) {
+		printk(KERN_ERR "%s: hot_debugfs_init error: %d\n",
+				__func__, ret);
+		goto failed_debugfs;
+	}
+
 	printk(KERN_INFO "VFS: Turning on hot data tracking\n");
 
 	return 0;
 
+failed_debugfs:
+	unregister_shrinker(&root->hot_shrink);
+	cancel_delayed_work_sync(&root->update_work);
+	destroy_workqueue(root->update_wq);
 failed_wq:
 	hot_map_array_exit(root);
 	hot_inode_tree_exit(root);
@@ -839,6 +1296,7 @@ void hot_track_exit(struct super_block *sb)
 	destroy_workqueue(root->update_wq);
 	hot_map_array_exit(root);
 	hot_inode_tree_exit(root);
+	hot_debugfs_exit(sb);
 	kfree(root);
 }
 EXPORT_SYMBOL_GPL(hot_track_exit);
diff --git a/fs/hot_tracking.h b/fs/hot_tracking.h
index b9d9717..6eb024f 100644
--- a/fs/hot_tracking.h
+++ b/fs/hot_tracking.h
@@ -87,6 +87,11 @@
 #define AVW_DIVIDER_POWER 40
 #define AVW_COEFF_POWER 0
 
+struct hot_debugfs {
+	const char *name;
+	const struct file_operations *fops;
+};
+
 struct hot_inode_item
 *hot_inode_item_find(struct hot_info *root, u64 ino);
 void hot_inode_item_put(struct hot_inode_item *he);
diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
index 66c434f..8913a4d 100644
--- a/include/linux/debugfs.h
+++ b/include/linux/debugfs.h
@@ -46,6 +46,9 @@ extern struct dentry *arch_debugfs_dir;
 extern const struct file_operations debugfs_file_operations;
 extern const struct inode_operations debugfs_link_operations;
 
+struct dentry *debugfs_get_dentry(const char *name,
+				struct dentry *parent, int len);
+
 struct dentry *debugfs_create_file(const char *name, umode_t mode,
 				   struct dentry *parent, void *data,
 				   const struct file_operations *fops);
@@ -103,6 +106,12 @@ bool debugfs_initialized(void);
 
 #include <linux/err.h>
 
+static inline struct dentry *debugfs_get_dentry(const char *name,
+					struct dentry *parent, int len)
+{
+	return ERR_PTR(-ENODEV);
+}
+
 /* 
  * We do not return NULL from these functions if CONFIG_DEBUG_FS is not enabled
  * so users have a chance to detect if there was a real error or not.  We don't
diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
index c81c331..7107cfa 100644
--- a/include/linux/hot_tracking.h
+++ b/include/linux/hot_tracking.h
@@ -97,6 +97,7 @@ struct hot_info {
 	struct workqueue_struct *update_wq;
 	struct delayed_work update_work;
 	struct shrinker hot_shrink;
+	struct dentry *debugfs_root;
 };
 
 /*
-- 
1.7.6.5

[RFC v4 12/15] vfs,hot_track: turn some Micro into be tunable

[zwu.kernel]

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

  Turn TIME_TO_KICK and HEAT_UPDATE_DELAY
into be tunable via /proc/sys/fs/hot-kick-time and
/proc/sys/fs/hot-update-delay.

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/hot_tracking.c            |   12 +++++++++---
 fs/hot_tracking.h            |    9 ---------
 include/linux/hot_tracking.h |    7 +++++++
 kernel/sysctl.c              |   14 ++++++++++++++
 4 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
index 18a64ee..15ed407 100644
--- a/fs/hot_tracking.c
+++ b/fs/hot_tracking.c
@@ -25,6 +25,12 @@
 #include <linux/limits.h>
 #include "hot_tracking.h"
 
+int sysctl_hot_kick_time __read_mostly = 300;
+EXPORT_SYMBOL_GPL(sysctl_hot_kick_time);
+
+int sysctl_hot_update_delay __read_mostly = 300;
+EXPORT_SYMBOL_GPL(sysctl_hot_update_delay);
+
 static struct hot_info *hot_root;
 
 /* kmem_cache pointers for slab caches */
@@ -345,7 +351,7 @@ static bool hot_freq_data_is_obsolete(struct hot_freq_data *freq_data)
 		(cur_time - timespec_to_ns(&freq_data->last_read_time));
 	u64 last_write_ns =
 		(cur_time - timespec_to_ns(&freq_data->last_write_time));
-	u64 kick_ns =  TIME_TO_KICK * NSEC_PER_SEC;
+	u64 kick_ns =  sysctl_hot_kick_time * NSEC_PER_SEC;
 
 	if ((last_read_ns > kick_ns) && (last_write_ns > kick_ns))
 		ret = 1;
@@ -651,7 +657,7 @@ static void hot_update_worker(struct work_struct *work)
 
 	/* Instert next delayed work */
 	queue_delayed_work(root->update_wq, &root->update_work,
-		msecs_to_jiffies(HEAT_UPDATE_DELAY * MSEC_PER_SEC));
+		msecs_to_jiffies(sysctl_hot_update_delay * MSEC_PER_SEC));
 }
 
 /*
@@ -1257,7 +1263,7 @@ int hot_track_init(struct super_block *sb)
 	/* Initialize hot tracking wq and arm one delayed work */
 	INIT_DELAYED_WORK(&root->update_work, hot_update_worker);
 	queue_delayed_work(root->update_wq, &root->update_work,
-		msecs_to_jiffies(HEAT_UPDATE_DELAY * MSEC_PER_SEC));
+		msecs_to_jiffies(sysctl_hot_update_delay * MSEC_PER_SEC));
 
 	/* Register a shrinker callback */
 	root->hot_shrink.shrink = hot_track_prune;
diff --git a/fs/hot_tracking.h b/fs/hot_tracking.h
index 6eb024f..d6d9161 100644
--- a/fs/hot_tracking.h
+++ b/fs/hot_tracking.h
@@ -26,15 +26,6 @@
 #define FREQ_POWER 4
 
 /*
- * time to quit keeping track of
- * tracking data (seconds)
- */
-#define TIME_TO_KICK 300
-
-/* set how often to update temperatures (seconds) */
-#define HEAT_UPDATE_DELAY 300
-
-/*
  * The following comments explain what exactly comprises a unit of heat.
  *
  * Each of six values of heat are calculated and combined in order to form an
diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
index 7107cfa..ea59f33 100644
--- a/include/linux/hot_tracking.h
+++ b/include/linux/hot_tracking.h
@@ -101,6 +101,13 @@ struct hot_info {
 };
 
 /*
+ * Two variables have meanings as below:
+ * 1. time to quit keeping track of tracking data (seconds)
+ * 2. set how often to update temperatures (seconds)
+ */
+extern int sysctl_hot_kick_time, sysctl_hot_update_delay;
+
+/*
  * Hot data tracking ioctls:
  *
  * HOT_INFO - retrieve info on frequency of access
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 26f65ea..37624fb 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1545,6 +1545,20 @@ static struct ctl_table fs_table[] = {
 		.proc_handler	= &pipe_proc_fn,
 		.extra1		= &pipe_min_size,
 	},
+	{
+		.procname	= "hot-kick-time",
+		.data		= &sysctl_hot_kick_time,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "hot-update-delay",
+		.data		= &sysctl_hot_update_delay,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
 	{ }
 };
 
-- 
1.7.6.5

[RFC v4 13/15] btrfs: add hot tracking support

[zwu.kernel]

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

  Introduce one new mount option '-o hot_track',
and add its parsing support.
  Its usage looks like:
   mount -o hot_track
   mount -o nouser,hot_track
   mount -o nouser,hot_track,loop
   mount -o hot_track,nouser

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/btrfs/ctree.h |    1 +
 fs/btrfs/super.c |   22 +++++++++++++++++++++-
 2 files changed, 22 insertions(+), 1 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 926c9ff..c3d28f0 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1756,6 +1756,7 @@ struct btrfs_ioctl_defrag_range_args {
 #define BTRFS_MOUNT_CHECK_INTEGRITY	(1 << 20)
 #define BTRFS_MOUNT_CHECK_INTEGRITY_INCLUDING_EXTENT_DATA (1 << 21)
 #define BTRFS_MOUNT_PANIC_ON_FATAL_ERROR	(1 << 22)
+#define BTRFS_MOUNT_HOT_TRACK		(1 << 23)
 
 #define btrfs_clear_opt(o, opt)		((o) &= ~BTRFS_MOUNT_##opt)
 #define btrfs_set_opt(o, opt)		((o) |= BTRFS_MOUNT_##opt)
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 915ac14..0bcc62b 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -41,6 +41,7 @@
 #include <linux/slab.h>
 #include <linux/cleancache.h>
 #include <linux/ratelimit.h>
+#include <linux/hot_tracking.h>
 #include "compat.h"
 #include "delayed-inode.h"
 #include "ctree.h"
@@ -299,6 +300,10 @@ static void btrfs_put_super(struct super_block *sb)
 	 * last process that kept it busy.  Or segfault in the aforementioned
 	 * process...  Whom would you report that to?
 	 */
+
+	/* Hot data tracking */
+	if (btrfs_test_opt(btrfs_sb(sb)->tree_root, HOT_TRACK))
+		hot_track_exit(sb);
 }
 
 enum {
@@ -311,7 +316,7 @@ enum {
 	Opt_enospc_debug, Opt_subvolrootid, Opt_defrag, Opt_inode_cache,
 	Opt_no_space_cache, Opt_recovery, Opt_skip_balance,
 	Opt_check_integrity, Opt_check_integrity_including_extent_data,
-	Opt_check_integrity_print_mask, Opt_fatal_errors,
+	Opt_check_integrity_print_mask, Opt_fatal_errors, Opt_hot_track,
 	Opt_err,
 };
 
@@ -352,6 +357,7 @@ static match_table_t tokens = {
 	{Opt_check_integrity_including_extent_data, "check_int_data"},
 	{Opt_check_integrity_print_mask, "check_int_print_mask=%d"},
 	{Opt_fatal_errors, "fatal_errors=%s"},
+	{Opt_hot_track, "hot_track"},
 	{Opt_err, NULL},
 };
 
@@ -614,6 +620,9 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 				goto out;
 			}
 			break;
+		case Opt_hot_track:
+			btrfs_set_opt(info->mount_opt, HOT_TRACK);
+			break;
 		case Opt_err:
 			printk(KERN_INFO "btrfs: unrecognized mount option "
 			       "'%s'\n", p);
@@ -841,11 +850,20 @@ static int btrfs_fill_super(struct super_block *sb,
 		goto fail_close;
 	}
 
+	if (btrfs_test_opt(fs_info->tree_root, HOT_TRACK)) {
+		err = hot_track_init(sb);
+		if (err)
+			goto fail_hot;
+	}
+
 	save_mount_options(sb, data);
 	cleancache_init_fs(sb);
 	sb->s_flags |= MS_ACTIVE;
 	return 0;
 
+fail_hot:
+	dput(sb->s_root);
+	sb->s_root = NULL;
 fail_close:
 	close_ctree(fs_info->tree_root);
 	return err;
@@ -941,6 +959,8 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",skip_balance");
 	if (btrfs_test_opt(root, PANIC_ON_FATAL_ERROR))
 		seq_puts(seq, ",fatal_errors=panic");
+	if (btrfs_test_opt(root, HOT_TRACK))
+		seq_puts(seq, ",hot_track");
 	return 0;
 }
 
-- 
1.7.6.5

[RFC v4 14/15] xfs: add hot tracking support

[zwu.kernel]

From: Dave Chinner <dchinner@redhat.com>

  Connect up the VFS hot tracking support
so XFS filesystems can make use of it.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_mount.h |    1 +
 fs/xfs/xfs_super.c |   16 ++++++++++++++++
 2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index deee09e..96d93c2 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -217,6 +217,7 @@ typedef struct xfs_mount {
 #define XFS_MOUNT_WSYNC		(1ULL << 0)	/* for nfs - all metadata ops
 						   must be synchronous except
 						   for space allocations */
+#define XFS_MOUNT_HOTTRACK      (1ULL << 1)     /* hot inode tracking */
 #define XFS_MOUNT_WAS_CLEAN	(1ULL << 3)
 #define XFS_MOUNT_FS_SHUTDOWN	(1ULL << 4)	/* atomic stop of all filesystem
 						   operations, typically for
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 26a09bd..48b3bed 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -61,6 +61,7 @@
 #include <linux/kthread.h>
 #include <linux/freezer.h>
 #include <linux/parser.h>
+#include <linux/hot_tracking.h>
 
 static const struct super_operations xfs_super_operations;
 static kmem_zone_t *xfs_ioend_zone;
@@ -114,6 +115,7 @@ mempool_t *xfs_ioend_pool;
 #define MNTOPT_NODELAYLOG  "nodelaylog"	/* Delayed logging disabled */
 #define MNTOPT_DISCARD	   "discard"	/* Discard unused blocks */
 #define MNTOPT_NODISCARD   "nodiscard"	/* Do not discard unused blocks */
+#define MNTOPT_HOTTRACK    "hot_track"  /* hot inode tracking */
 
 /*
  * Table driven mount option parser.
@@ -371,6 +373,8 @@ xfs_parseargs(
 			mp->m_flags |= XFS_MOUNT_DISCARD;
 		} else if (!strcmp(this_char, MNTOPT_NODISCARD)) {
 			mp->m_flags &= ~XFS_MOUNT_DISCARD;
+		} else if (!strcmp(this_char, MNTOPT_HOTTRACK)) {
+			mp->m_flags |= XFS_MOUNT_HOTTRACK;
 		} else if (!strcmp(this_char, "ihashsize")) {
 			xfs_warn(mp,
 	"ihashsize no longer used, option is deprecated.");
@@ -1005,6 +1009,9 @@ xfs_fs_put_super(
 {
 	struct xfs_mount	*mp = XFS_M(sb);
 
+	if (mp->m_flags & XFS_MOUNT_HOTTRACK)
+		hot_track_exit(sb);
+
 	xfs_filestream_unmount(mp);
 	cancel_delayed_work_sync(&mp->m_sync_work);
 	xfs_unmountfs(mp);
@@ -1407,7 +1414,16 @@ xfs_fs_fill_super(
 		goto out_unmount;
 	}
 
+	if (mp->m_flags & XFS_MOUNT_HOTTRACK) {
+		error = hot_track_init(sb);
+		if (error)
+			goto out_free_root;
+	}
+
 	return 0;
+ out_free_root:
+	dput(sb->s_root);
+	sb->s_root = NULL;
  out_syncd_stop:
 	xfs_syncd_stop(mp);
  out_filestream_unmount:
-- 
1.7.6.5

[RFC v4 15/15] vfs,hot_track: add the documentation

[zwu.kernel]

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

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 Documentation/filesystems/00-INDEX         |    2 +
 Documentation/filesystems/hot_tracking.txt |  164 ++++++++++++++++++++++++++++
 2 files changed, 166 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/filesystems/hot_tracking.txt

diff --git a/Documentation/filesystems/00-INDEX b/Documentation/filesystems/00-INDEX
index 8c624a1..b68bdff 100644
--- a/Documentation/filesystems/00-INDEX
+++ b/Documentation/filesystems/00-INDEX
@@ -118,3 +118,5 @@ xfs.txt
 	- info and mount options for the XFS filesystem.
 xip.txt
 	- info on execute-in-place for file mappings.
+hot_tracking.txt
+	- info on hot data tracking in VFS layer
diff --git a/Documentation/filesystems/hot_tracking.txt b/Documentation/filesystems/hot_tracking.txt
new file mode 100644
index 0000000..ccb367d
--- /dev/null
+++ b/Documentation/filesystems/hot_tracking.txt
@@ -0,0 +1,164 @@
+Hot Data Tracking
+
+September, 2012		Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
+
+CONTENTS
+
+1. Introduction
+2. Motivation
+3. The Design
+4. Git Development Tree
+5. Usage Example
+
+
+1. Introduction
+
+  The feature adds experimental support for tracking data temperature
+information in VFS layer.  Essentially, this means maintaining some key
+stats(like number of reads/writes, last read/write time, frequency of
+reads/writes), then distilling those numbers down to a single
+"temperature" value that reflects what data is "hot," and using that
+temperature to move data to SSDs.
+
+  The long-term goal of the feature is to allow some FSs,
+e.g. Btrfs to intelligently utilize SSDs in a heterogenous volume.
+Incidentally, this project has been motivated by
+the Project Ideas page on the Btrfs wiki.
+
+  Of course, users are warned not to run this code outside of development
+environments. These patches are EXPERIMENTAL, and as such they might eat
+your data and/or memory. That said, the code should be relatively safe
+when the hottrack mount option are disabled.
+
+2. Motivation
+
+  The overall goal of enabling hot data relocation to SSD has been
+motivated by the Project Ideas page on the Btrfs wiki at
+<https://btrfs.wiki.kernel.org/index.php/Project_ideas>.
+It will divide into two steps. VFS provide hot data tracking function
+while specific FS will provide hot data relocation function.
+So as the first step of this goal, it is hoped that the patchset
+for hot data tracking will eventually mature into VFS.
+
+  This is essentially the traditional cache argument: SSD is fast and
+expensive; HDD is cheap but slow. ZFS, for example, can already take
+advantage of SSD caching. Btrfs should also be able to take advantage of
+hybrid storage without many broad, sweeping changes to existing code.
+
+
+3. The Design
+
+These include the following parts:
+
+    * Hooks in existing vfs functions to track data access frequency
+
+    * New radix-trees for tracking access frequency of inodes and sub-file
+ranges
+    The relationship between super_block and radix-tree is as below:
+hot_info.hot_inode_tree
+    Each FS instance can find hot tracking info s_hotinfo.
+In this hot_info, it store a lot of hot tracking info such as hot_inode_tree,
+inode and range list, etc.
+
+    * A list for indexing data by its temperature
+
+    * A debugfs interface for dumping data from the radix-trees
+
+    * A background kthread for updating inode heat info
+
+    * Mount options for enabling temperature tracking(-o hot_track,
+default mean disabled)
+    * An ioctl to retrieve the frequency information collected for a certain
+file
+    * Ioctls to enable/disable frequency tracking per inode.
+
+Let us see their relationship as below:
+
+    * hot_info.hot_inode_tree indexes hot_inode_items, one per inode
+
+    * hot_inode_item contains access frequency data for that inode
+
+    * hot_inode_item holds a heat list node to index the access
+frequency data for that inode
+
+    * hot_inode_item.hot_range_tree indexes hot_range_items for that inode
+
+    * hot_range_item contains access frequency data for that range
+
+    * hot_range_item holds a heat list node to index the access
+frequency data for that range
+
+    * hot_info.heat_inode_map indexes per-inode heat list nodes
+
+    * hot_info.heat_range_map indexes per-range heat list nodes
+
+  How about some ascii art? :) Just looking at the hot inode item case
+(the range item case is the same pattern, though), we have:
+
+heat_inode_map           hot_inode_tree
+    |                         |
+    |                         V
+    |           +-------hot_comm_item--------+
+    |           |       frequency data       |
++---+           |        list_head           |
+|               V            ^ |             V
+| ...<--hot_comm_item-->...  | |  ...<--hot_comm_item-->...
+|       frequency data       | |        frequency data
++-------->list_head----------+ +--------->list_head--->.....
+       hot_range_tree                  hot_range_tree
+                                             |
+             heat_range_map                  V
+                   |           +-------hot_comm_item--------+
+                   |           |       frequency data       |
+               +---+           |        list_head           |
+               |               V            ^ |             V
+               | ...<--hot_comm_item-->...  | |  ...<--hot_comm_item-->...
+               |       frequency data       | |        frequency data
+               +-------->list_head----------+ +--------->list_head--->.....
+
+4. Git Development Tree
+
+  The feature is still on development and review, so if you're interested,
+you can pull from the git repository at the following location:
+  https://github.com/wuzhy/kernel.git hot_tracking
+  git://github.com/wuzhy/kernel.git hot_tracking
+
+
+5. Usage Example
+
+To use hot tracking, you should mount like this:
+
+$ mount -o hot_track /dev/sdb /mnt
+[ 1505.894078] device label test devid 1 transid 29 /dev/sdb
+[ 1505.952977] btrfs: disk space caching is enabled
+[ 1506.069678] vfs: turning on hot data tracking
+
+Mount debugfs at first:
+
+$ mount -t debugfs none /sys/kernel/debug
+$ ls -l /sys/kernel/debug/hot_track/
+total 0
+drwxr-xr-x 2 root root 0 Aug  8 04:40 sdb
+$ ls -l /sys/kernel/debug/hot_track/sdb
+total 0
+-rw-r--r-- 1 root root 0 Aug  8 04:40 inode_data
+-rw-r--r-- 1 root root 0 Aug  8 04:40 range_data
+
+View information about hot tracking from debugfs:
+
+$ echo "hot tracking test" > /mnt/file
+$ cat /sys/kernel/debug/hot_track/sdb/inode_data
+inode #279, reads 0, writes 1, avg read time 18446744073709551615,
+avg write time 5251566408153596, temp 109
+$ cat /sys/kernel/debug/hot_track/sdb/range_data
+inode #279, range start 0 (range len 1048576) reads 0, writes 1,
+avg read time 18446744073709551615, avg write time 1128690176623144209, temp 64
+
+$ echo "hot data tracking test" >> /mnt/file
+$ cat /sys/kernel/debug/hot_track/sdb/inode_data
+inode #279, reads 0, writes 2, avg read time 18446744073709551615,
+avg write time 4923343766042451, temp 109
+$ cat /sys/kernel/debug/hot_track/sdb/range_data
+inode #279, range start 0 (range len 1048576) reads 0, writes 2,
+avg read time 18446744073709551615, avg write time 1058147040842596150, temp 64
+
-- 
1.7.6.5

Re: [RFC v4 03/15] vfs,hot_track: add the function for collecting I/O frequency

[Zheng Liu]

Hi Zhiyong, 

On Thu, Oct 25, 2012 at 11:08:55PM +0800, zwu.kernel@gmail.com wrote:
[snip]
> @@ -199,6 +342,54 @@ err:
>  }
>  
>  /*
> + * Main function to update access frequency from read/writepage(s) hooks
> + */
> +inline void hot_update_freqs(struct inode *inode, u64 start,
> +			u64 len, int rw)

This function seems too big.  So we really need to inline this function?

Regards,
Zheng

> +{
> +	struct hot_info *root = inode->i_sb->s_hot_root;
> +	struct hot_inode_item *he;
> +	struct hot_range_item *hr;
> +	u32 cur, end;
> +
> +	if (!root || (len == 0))
> +		return;
> +
> +	he = hot_inode_item_find(root, inode->i_ino);
> +	if (IS_ERR(he)) {
> +		WARN_ON(1);
> +		return;
> +	}
> +
> +	spin_lock(&he->hot_inode.lock);
> +	hot_freq_data_update(&he->hot_inode.hot_freq_data, rw);
> +	spin_unlock(&he->hot_inode.lock);
> +
> +	/*
> +	 * Align ranges on RANGE_SIZE boundary
> +	 * to prevent proliferation of range structs
> +	 */
> +	end = (start + len + RANGE_SIZE - 1) >> RANGE_BITS;
> +	for (cur = (start >> RANGE_BITS); cur < end; cur++) {
> +		hr = hot_range_item_find(he, cur);
> +		if (IS_ERR(hr)) {
> +			WARN_ON(1);
> +			hot_inode_item_put(he);
> +			return;
> +		}
> +
> +		spin_lock(&hr->hot_range.lock);
> +		hot_freq_data_update(&hr->hot_range.hot_freq_data, rw);
> +		spin_unlock(&hr->hot_range.lock);
> +
> +		hot_range_item_put(hr);
> +	}
> +
> +	hot_inode_item_put(he);
> +}
> +EXPORT_SYMBOL_GPL(hot_update_freqs);

[PATCH] ext4: add hot tracking support

[Zheng Liu]

From: Zheng Liu <wenqing.lz@taobao.com>

Define a new mount option to add VFS hot tracking support in order to use it in
ext4.

CC: Zhi Yong Wu <zwu.kernel@gmail.com>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
---
Hi Zhiyong,

Here is a try to add hot tracking support in ext4.  I do some simple tests and
it works well.

Regards,
Zheng

 fs/ext4/ext4.h  |  3 +++
 fs/ext4/super.c | 15 ++++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 3c20de1..f6cff1e 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1298,6 +1298,9 @@ struct ext4_sb_info {
 
 	/* Precomputed FS UUID checksum for seeding other checksums */
 	__u32 s_csum_seed;
+
+	/* Enable hot tracking or not */
+	int s_hottrack_enable;
 };
 
 static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 80928f7..1506dc3 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -43,6 +43,7 @@
 
 #include <linux/kthread.h>
 #include <linux/freezer.h>
+#include <linux/hot_tracking.h>
 
 #include "ext4.h"
 #include "ext4_extents.h"
@@ -864,6 +865,8 @@ static void ext4_put_super(struct super_block *sb)
 	ext4_ext_release(sb);
 	ext4_xattr_put_super(sb);
 
+	if (sbi->s_hottrack_enable)
+		hot_track_exit(sb);
 	if (!(sb->s_flags & MS_RDONLY)) {
 		EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
 		es->s_state = cpu_to_le16(sbi->s_mount_state);
@@ -1222,7 +1225,7 @@ enum {
 	Opt_inode_readahead_blks, Opt_journal_ioprio,
 	Opt_dioread_nolock, Opt_dioread_lock,
 	Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable,
-	Opt_max_dir_size_kb,
+	Opt_max_dir_size_kb, Opt_hottrack,
 };
 
 static const match_table_t tokens = {
@@ -1297,6 +1300,7 @@ static const match_table_t tokens = {
 	{Opt_init_itable, "init_itable"},
 	{Opt_noinit_itable, "noinit_itable"},
 	{Opt_max_dir_size_kb, "max_dir_size_kb=%u"},
+	{Opt_hottrack, "hot_track"},
 	{Opt_removed, "check=none"},	/* mount option from ext2/3 */
 	{Opt_removed, "nocheck"},	/* mount option from ext2/3 */
 	{Opt_removed, "reservation"},	/* mount option from ext2/3 */
@@ -1478,6 +1482,7 @@ static const struct mount_opts {
 	{Opt_jqfmt_vfsv0, QFMT_VFS_V0, MOPT_QFMT},
 	{Opt_jqfmt_vfsv1, QFMT_VFS_V1, MOPT_QFMT},
 	{Opt_max_dir_size_kb, 0, MOPT_GTE0},
+	{Opt_hottrack, 0, MOPT_GTE0},
 	{Opt_err, 0, 0}
 };
 
@@ -1595,6 +1600,14 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
 			sbi->s_li_wait_mult = arg;
 		} else if (token == Opt_max_dir_size_kb) {
 			sbi->s_max_dir_size_kb = arg;
+		} else if (token == Opt_hottrack) {
+			if (hot_track_init(sb)) {
+				ext4_msg(sb, KERN_ERR,
+					 "EXT4-fs: hot tracking initialization"
+					 " failed");
+				return -1;
+			}
+			sbi->s_hottrack_enable = 1;
 		} else if (token == Opt_stripe) {
 			sbi->s_stripe = arg;
 		} else if (m->flags & MOPT_DATAJ) {
-- 
1.7.12.rc2.18.g61b472e

Re: [PATCH] ext4: add hot tracking support

[Zhi Yong Wu]

On Sun, Oct 28, 2012 at 5:22 PM, Zheng Liu <gnehzuil.liu@gmail.com> wrote:
> From: Zheng Liu <wenqing.lz@taobao.com>
>
> Define a new mount option to add VFS hot tracking support in order to use it in
> ext4.
>
> CC: Zhi Yong Wu <zwu.kernel@gmail.com>
> Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
> ---
> Hi Zhiyong,
>
> Here is a try to add hot tracking support in ext4.  I do some simple tests and
> it works well.
>
> Regards,
> Zheng
>
>  fs/ext4/ext4.h  |  3 +++
>  fs/ext4/super.c | 15 ++++++++++++++-
>  2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 3c20de1..f6cff1e 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1298,6 +1298,9 @@ struct ext4_sb_info {
>
>         /* Precomputed FS UUID checksum for seeding other checksums */
>         __u32 s_csum_seed;
> +
> +       /* Enable hot tracking or not */
> +       int s_hottrack_enable;
>  };
>
>  static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 80928f7..1506dc3 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -43,6 +43,7 @@
>
>  #include <linux/kthread.h>
>  #include <linux/freezer.h>
> +#include <linux/hot_tracking.h>
>
>  #include "ext4.h"
>  #include "ext4_extents.h"
> @@ -864,6 +865,8 @@ static void ext4_put_super(struct super_block *sb)
>         ext4_ext_release(sb);
>         ext4_xattr_put_super(sb);
>
> +       if (sbi->s_hottrack_enable)
> +               hot_track_exit(sb);
>         if (!(sb->s_flags & MS_RDONLY)) {
>                 EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
>                 es->s_state = cpu_to_le16(sbi->s_mount_state);
> @@ -1222,7 +1225,7 @@ enum {
>         Opt_inode_readahead_blks, Opt_journal_ioprio,
>         Opt_dioread_nolock, Opt_dioread_lock,
>         Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable,
> -       Opt_max_dir_size_kb,
> +       Opt_max_dir_size_kb, Opt_hottrack,
>  };
>
>  static const match_table_t tokens = {
> @@ -1297,6 +1300,7 @@ static const match_table_t tokens = {
>         {Opt_init_itable, "init_itable"},
>         {Opt_noinit_itable, "noinit_itable"},
>         {Opt_max_dir_size_kb, "max_dir_size_kb=%u"},
> +       {Opt_hottrack, "hot_track"},
>         {Opt_removed, "check=none"},    /* mount option from ext2/3 */
>         {Opt_removed, "nocheck"},       /* mount option from ext2/3 */
>         {Opt_removed, "reservation"},   /* mount option from ext2/3 */
> @@ -1478,6 +1482,7 @@ static const struct mount_opts {
>         {Opt_jqfmt_vfsv0, QFMT_VFS_V0, MOPT_QFMT},
>         {Opt_jqfmt_vfsv1, QFMT_VFS_V1, MOPT_QFMT},
>         {Opt_max_dir_size_kb, 0, MOPT_GTE0},
> +       {Opt_hottrack, 0, MOPT_GTE0},
>         {Opt_err, 0, 0}
>  };
>
> @@ -1595,6 +1600,14 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
>                         sbi->s_li_wait_mult = arg;
>                 } else if (token == Opt_max_dir_size_kb) {
>                         sbi->s_max_dir_size_kb = arg;
> +               } else if (token == Opt_hottrack) {
> +                       if (hot_track_init(sb)) {
> +                               ext4_msg(sb, KERN_ERR,
> +                                        "EXT4-fs: hot tracking initialization"
> +                                        " failed");
> +                               return -1;
> +                       }
> +                       sbi->s_hottrack_enable = 1;
>                 } else if (token == Opt_stripe) {
>                         sbi->s_stripe = arg;
>                 } else if (m->flags & MOPT_DATAJ) {
HI, Zheng,

Do you not need to free stuff related to hot tracking when umount?

> --
> 1.7.12.rc2.18.g61b472e
>



-- 
Regards,

Zhi Yong Wu

Re: [RFC v4 03/15] vfs,hot_track: add the function for collecting I/O frequency

[Zhi Yong Wu]

On Sun, Oct 28, 2012 at 3:55 PM, Zheng Liu <gnehzuil.liu@gmail.com> wrote:
> Hi Zhiyong,
>
> On Thu, Oct 25, 2012 at 11:08:55PM +0800, zwu.kernel@gmail.com wrote:
> [snip]
>> @@ -199,6 +342,54 @@ err:
>>  }
>>
>>  /*
>> + * Main function to update access frequency from read/writepage(s) hooks
>> + */
>> +inline void hot_update_freqs(struct inode *inode, u64 start,
>> +                     u64 len, int rw)
>
> This function seems too big.  So we really need to inline this function?
As Dave said in his comments, it will add a function call
overhead even when tracking is not enabled. a static inline function
will just result in no extra overhead other than the if
statement....

>
> Regards,
> Zheng
>
>> +{
>> +     struct hot_info *root = inode->i_sb->s_hot_root;
>> +     struct hot_inode_item *he;
>> +     struct hot_range_item *hr;
>> +     u32 cur, end;
>> +
>> +     if (!root || (len == 0))
>> +             return;
>> +
>> +     he = hot_inode_item_find(root, inode->i_ino);
>> +     if (IS_ERR(he)) {
>> +             WARN_ON(1);
>> +             return;
>> +     }
>> +
>> +     spin_lock(&he->hot_inode.lock);
>> +     hot_freq_data_update(&he->hot_inode.hot_freq_data, rw);
>> +     spin_unlock(&he->hot_inode.lock);
>> +
>> +     /*
>> +      * Align ranges on RANGE_SIZE boundary
>> +      * to prevent proliferation of range structs
>> +      */
>> +     end = (start + len + RANGE_SIZE - 1) >> RANGE_BITS;
>> +     for (cur = (start >> RANGE_BITS); cur < end; cur++) {
>> +             hr = hot_range_item_find(he, cur);
>> +             if (IS_ERR(hr)) {
>> +                     WARN_ON(1);
>> +                     hot_inode_item_put(he);
>> +                     return;
>> +             }
>> +
>> +             spin_lock(&hr->hot_range.lock);
>> +             hot_freq_data_update(&hr->hot_range.hot_freq_data, rw);
>> +             spin_unlock(&hr->hot_range.lock);
>> +
>> +             hot_range_item_put(hr);
>> +     }
>> +
>> +     hot_inode_item_put(he);
>> +}
>> +EXPORT_SYMBOL_GPL(hot_update_freqs);



-- 
Regards,

Zhi Yong Wu

Re: [RFC v4 03/15] vfs,hot_track: add the function for collecting I/O frequency

[Dave Chinner]

On Sun, Oct 28, 2012 at 09:51:48PM +0800, Zhi Yong Wu wrote:
> On Sun, Oct 28, 2012 at 3:55 PM, Zheng Liu <gnehzuil.liu@gmail.com> wrote:
> > Hi Zhiyong,
> >
> > On Thu, Oct 25, 2012 at 11:08:55PM +0800, zwu.kernel@gmail.com wrote:
> > [snip]
> >> @@ -199,6 +342,54 @@ err:
> >>  }
> >>
> >>  /*
> >> + * Main function to update access frequency from read/writepage(s) hooks
> >> + */
> >> +inline void hot_update_freqs(struct inode *inode, u64 start,
> >> +                     u64 len, int rw)
> >
> > This function seems too big.  So we really need to inline this function?
> As Dave said in his comments, it will add a function call
> overhead even when tracking is not enabled. a static inline function
> will just result in no extra overhead other than the if
> statement....

I don't think I said that with respect to this code. I think I said
it w.r.t. a define or a small wrapper that decides to call
hot_update_freqs().  A static inline fucntion should only be a
couple of lines of code at most.

A static function, OTOH, can be inlined by the compiler if the
compiler thinks that is a win. But....

.....

> >> +EXPORT_SYMBOL_GPL(hot_update_freqs);

... it's an exported function, so it can't be inline or static, so
using "inline" is wrong whatever way you look at it. ;)

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

Re: [RFC v4 03/15] vfs,hot_track: add the function for collecting I/O frequency

[Zhi Yong Wu]

On Mon, Oct 29, 2012 at 10:01 AM, Dave Chinner <david@fromorbit.com> wrote:
> On Sun, Oct 28, 2012 at 09:51:48PM +0800, Zhi Yong Wu wrote:
>> On Sun, Oct 28, 2012 at 3:55 PM, Zheng Liu <gnehzuil.liu@gmail.com> wrote:
>> > Hi Zhiyong,
>> >
>> > On Thu, Oct 25, 2012 at 11:08:55PM +0800, zwu.kernel@gmail.com wrote:
>> > [snip]
>> >> @@ -199,6 +342,54 @@ err:
>> >>  }
>> >>
>> >>  /*
>> >> + * Main function to update access frequency from read/writepage(s) hooks
>> >> + */
>> >> +inline void hot_update_freqs(struct inode *inode, u64 start,
>> >> +                     u64 len, int rw)
>> >
>> > This function seems too big.  So we really need to inline this function?
>> As Dave said in his comments, it will add a function call
>> overhead even when tracking is not enabled. a static inline function
>> will just result in no extra overhead other than the if
>> statement....
>
> I don't think I said that with respect to this code. I think I said
> it w.r.t. a define or a small wrapper that decides to call
> hot_update_freqs().  A static inline fucntion should only be a
> couple of lines of code at most.
>
> A static function, OTOH, can be inlined by the compiler if the
> compiler thinks that is a win. But....
thanks for your explaination at first.
>
> .....
>
>> >> +EXPORT_SYMBOL_GPL(hot_update_freqs);
>
> ... it's an exported function, so it can't be inline or static, so
> using "inline" is wrong whatever way you look at it. ;)
ah, but i' m surprised by why the compiler find this error.

>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@fromorbit.com
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html



-- 
Regards,

Zhi Yong Wu

Re: [PATCH] ext4: add hot tracking support

[Zhi Yong Wu]

On Mon, Oct 29, 2012 at 10:32 AM, Zheng Liu <gnehzuil.liu@gmail.com> wrote:
> On Sun, Oct 28, 2012 at 09:45:49PM +0800, Zhi Yong Wu wrote:
> [snip]
>> On Sun, Oct 28, 2012 at 5:22 PM, Zheng Liu <gnehzuil.liu@gmail.com> wrote:
>> > @@ -864,6 +865,8 @@ static void ext4_put_super(struct super_block *sb)
>> >         ext4_ext_release(sb);
>> >         ext4_xattr_put_super(sb);
>> >
>> > +       if (sbi->s_hottrack_enable)
>> > +               hot_track_exit(sb);
>> >         if (!(sb->s_flags & MS_RDONLY)) {
>> >                 EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
>> >                 es->s_state = cpu_to_le16(sbi->s_mount_state);
>> HI, Zheng,
>>
>> Do you not need to free stuff related to hot tracking when umount?
>
> I call hot_track_exit() in put_super callback function.  I have no idea
> that there still has some other functions that need to be called.  Am I
> missing something?
You are right....
>
> Regards,
> Zheng



-- 
Regards,

Zhi Yong Wu

Re: [PATCH] ext4: add hot tracking support

[Zheng Liu]

On Sun, Oct 28, 2012 at 09:45:49PM +0800, Zhi Yong Wu wrote:
[snip]
> On Sun, Oct 28, 2012 at 5:22 PM, Zheng Liu <gnehzuil.liu@gmail.com> wrote:
> > @@ -864,6 +865,8 @@ static void ext4_put_super(struct super_block *sb)
> >         ext4_ext_release(sb);
> >         ext4_xattr_put_super(sb);
> >
> > +       if (sbi->s_hottrack_enable)
> > +               hot_track_exit(sb);
> >         if (!(sb->s_flags & MS_RDONLY)) {
> >                 EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
> >                 es->s_state = cpu_to_le16(sbi->s_mount_state);
> HI, Zheng,
> 
> Do you not need to free stuff related to hot tracking when umount?

I call hot_track_exit() in put_super callback function.  I have no idea
that there still has some other functions that need to be called.  Am I
missing something?

Regards,
Zheng

Re: [PATCH] ext4: add hot tracking support

[Zhi Yong Wu]

HI, Zheng,

I guess that you should add some hot tracking stuff in some
ext4_show_xxx function, right?

On Sun, Oct 28, 2012 at 5:22 PM, Zheng Liu <gnehzuil.liu@gmail.com> wrote:
> From: Zheng Liu <wenqing.lz@taobao.com>
>
> Define a new mount option to add VFS hot tracking support in order to use it in
> ext4.
>
> CC: Zhi Yong Wu <zwu.kernel@gmail.com>
> Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
> ---
> Hi Zhiyong,
>
> Here is a try to add hot tracking support in ext4.  I do some simple tests and
> it works well.
>
> Regards,
> Zheng
>
>  fs/ext4/ext4.h  |  3 +++
>  fs/ext4/super.c | 15 ++++++++++++++-
>  2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 3c20de1..f6cff1e 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1298,6 +1298,9 @@ struct ext4_sb_info {
>
>         /* Precomputed FS UUID checksum for seeding other checksums */
>         __u32 s_csum_seed;
> +
> +       /* Enable hot tracking or not */
> +       int s_hottrack_enable;
>  };
>
>  static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 80928f7..1506dc3 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -43,6 +43,7 @@
>
>  #include <linux/kthread.h>
>  #include <linux/freezer.h>
> +#include <linux/hot_tracking.h>
>
>  #include "ext4.h"
>  #include "ext4_extents.h"
> @@ -864,6 +865,8 @@ static void ext4_put_super(struct super_block *sb)
>         ext4_ext_release(sb);
>         ext4_xattr_put_super(sb);
>
> +       if (sbi->s_hottrack_enable)
> +               hot_track_exit(sb);
>         if (!(sb->s_flags & MS_RDONLY)) {
>                 EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
>                 es->s_state = cpu_to_le16(sbi->s_mount_state);
> @@ -1222,7 +1225,7 @@ enum {
>         Opt_inode_readahead_blks, Opt_journal_ioprio,
>         Opt_dioread_nolock, Opt_dioread_lock,
>         Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable,
> -       Opt_max_dir_size_kb,
> +       Opt_max_dir_size_kb, Opt_hottrack,
>  };
>
>  static const match_table_t tokens = {
> @@ -1297,6 +1300,7 @@ static const match_table_t tokens = {
>         {Opt_init_itable, "init_itable"},
>         {Opt_noinit_itable, "noinit_itable"},
>         {Opt_max_dir_size_kb, "max_dir_size_kb=%u"},
> +       {Opt_hottrack, "hot_track"},
>         {Opt_removed, "check=none"},    /* mount option from ext2/3 */
>         {Opt_removed, "nocheck"},       /* mount option from ext2/3 */
>         {Opt_removed, "reservation"},   /* mount option from ext2/3 */
> @@ -1478,6 +1482,7 @@ static const struct mount_opts {
>         {Opt_jqfmt_vfsv0, QFMT_VFS_V0, MOPT_QFMT},
>         {Opt_jqfmt_vfsv1, QFMT_VFS_V1, MOPT_QFMT},
>         {Opt_max_dir_size_kb, 0, MOPT_GTE0},
> +       {Opt_hottrack, 0, MOPT_GTE0},
>         {Opt_err, 0, 0}
>  };
>
> @@ -1595,6 +1600,14 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
>                         sbi->s_li_wait_mult = arg;
>                 } else if (token == Opt_max_dir_size_kb) {
>                         sbi->s_max_dir_size_kb = arg;
> +               } else if (token == Opt_hottrack) {
> +                       if (hot_track_init(sb)) {
> +                               ext4_msg(sb, KERN_ERR,
> +                                        "EXT4-fs: hot tracking initialization"
> +                                        " failed");
> +                               return -1;
> +                       }
> +                       sbi->s_hottrack_enable = 1;
>                 } else if (token == Opt_stripe) {
>                         sbi->s_stripe = arg;
>                 } else if (m->flags & MOPT_DATAJ) {
> --
> 1.7.12.rc2.18.g61b472e
>



-- 
Regards,

Zhi Yong Wu