[PATCH v2 02/12] VFS hot tracking: add i/o freq tracking hooks

From: zwu . kernel
Date: Mon May 13 2013 - 20:59:15 EST

From: Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx>

Add i/o freq tracking hooks in real read/write code paths
which include read_pages(), do_writepages(), do_generic_file_read(),
and __blockdev_direct_IO().
Currently whole FS has one RB tree to track i/o freqs for
all inodes which had real disk i/o, while every inode has its
own one RB tree to track i/o freqs for all of its extents.
When real disk i/o for the inode are done, its own i/o freq will
be created or updated in the RB tree per FS, and the i/o freq for
all of its extents will also be done in the RB-tree per inode.
Also, Each of the two structures hot_inode_item and hot_range_item
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: Chandra Seetharaman <sekharan@xxxxxxxxxx>
Signed-off-by: Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx>
---
fs/direct-io.c | 5 +
fs/hot_tracking.c | 284 +++++++++++++++++++++++++++++++++++++++++++
fs/hot_tracking.h | 4 +
fs/namei.c | 2 +
include/linux/hot_tracking.h | 17 +++
mm/filemap.c | 6 +
mm/page-writeback.c | 12 ++
mm/readahead.c | 6 +
8 files changed, 336 insertions(+)

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 7ab90f5..6cb0598 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -38,6 +38,7 @@
#include <linux/atomic.h>
#include <linux/prefetch.h>
#include <linux/aio.h>
+#include "hot_tracking.h"

/*
* How many user pages to map in one call to get_user_pages(). This determines
@@ -1295,6 +1296,10 @@ __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, offset, 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/fs/hot_tracking.c b/fs/hot_tracking.c
index 6bf4229..cc899f4 100644
--- a/fs/hot_tracking.c
+++ b/fs/hot_tracking.c
@@ -26,6 +26,26 @@ static struct kmem_cache *hot_range_item_cachep __read_mostly;

static void hot_inode_item_free(struct kref *kref);

+static void hot_comm_item_init(struct hot_comm_item *ci, int type)
+{
+ kref_init(&ci->refs);
+ clear_bit(HOT_DELETING, &ci->delete_flag);
+ memset(&ci->hot_freq_data, 0, sizeof(struct hot_freq_data));
+ ci->hot_freq_data.avg_delta_reads = (u64) -1;
+ ci->hot_freq_data.avg_delta_writes = (u64) -1;
+ ci->hot_freq_data.flags = type;
+}
+
+static void hot_range_item_init(struct hot_range_item *hr,
+ struct hot_inode_item *he, loff_t start)
+{
+ hr->start = start;
+ hr->len = hot_shift(1, RANGE_BITS, true);
+ hr->hot_inode = he;
+ hr->storage_type = -1;
+ hot_comm_item_init(&hr->hot_range, TYPE_RANGE);
+}
+
static void hot_comm_item_free_cb(struct rcu_head *head)
{
struct hot_comm_item *ci = container_of(head,
@@ -65,10 +85,27 @@ void hot_comm_item_put(struct hot_comm_item *ci)
}
EXPORT_SYMBOL_GPL(hot_comm_item_put);

+/*
+ * root->t_lock or he->i_lock is acquired in this function
+ */
static void hot_comm_item_unlink(struct hot_info *root,
struct hot_comm_item *ci)
{
if (!test_and_set_bit(HOT_DELETING, &ci->delete_flag)) {
+ if (ci->hot_freq_data.flags == TYPE_RANGE) {
+ struct hot_range_item *hr = container_of(ci,
+ struct hot_range_item, hot_range);
+ struct hot_inode_item *he = hr->hot_inode;
+
+ spin_lock(&he->i_lock);
+ rb_erase(&ci->rb_node, &he->hot_range_tree);
+ spin_unlock(&he->i_lock);
+ } else {
+ spin_lock(&root->t_lock);
+ rb_erase(&ci->rb_node, &root->hot_inode_tree);
+ spin_unlock(&root->t_lock);
+ }
+
hot_comm_item_put(ci);
}
}
@@ -94,6 +131,15 @@ static void hot_range_tree_free(struct hot_inode_item *he)

}

+static void hot_inode_item_init(struct hot_inode_item *he,
+ struct hot_info *hot_root, u64 ino)
+{
+ he->i_ino = ino;
+ he->hot_root = hot_root;
+ spin_lock_init(&he->i_lock);
+ hot_comm_item_init(&he->hot_inode, TYPE_INODE);
+}
+
static void hot_inode_item_free(struct kref *kref)
{
struct hot_comm_item *ci = container_of(kref,
@@ -107,6 +153,195 @@ static void hot_inode_item_free(struct kref *kref)
call_rcu(&he->hot_inode.c_rcu, hot_comm_item_free_cb);
}

+/* root->t_lock is acquired in this function. */
+struct hot_inode_item
+*hot_inode_item_lookup(struct hot_info *root, u64 ino, int alloc)
+{
+ struct rb_node **p;
+ struct rb_node *parent = NULL;
+ struct hot_comm_item *ci;
+ struct hot_inode_item *he, *he_new = NULL;
+
+ /* walk tree to find insertion point */
+redo:
+ spin_lock(&root->t_lock);
+ p = &root->hot_inode_tree.rb_node;
+ while (*p) {
+ parent = *p;
+ ci = rb_entry(parent, struct hot_comm_item, rb_node);
+ he = container_of(ci, struct hot_inode_item, hot_inode);
+ if (ino < he->i_ino)
+ p = &(*p)->rb_left;
+ else if (ino > he->i_ino)
+ p = &(*p)->rb_right;
+ else {
+ hot_comm_item_get(&he->hot_inode);
+ spin_unlock(&root->t_lock);
+ if (he_new)
+ /*
+ * Lost the race. Somebody else inserted
+ * the item for the inode. Free the
+ * newly allocated item.
+ */
+ kmem_cache_free(hot_inode_item_cachep, he_new);
+
+ if (test_bit(HOT_DELETING, &he->hot_inode.delete_flag))
+ return ERR_PTR(-ENOENT);
+
+ return he;
+ }
+ }
+
+ if (he_new) {
+ rb_link_node(&he_new->hot_inode.rb_node, parent, p);
+ rb_insert_color(&he_new->hot_inode.rb_node,
+ &root->hot_inode_tree);
+ hot_comm_item_get(&he_new->hot_inode);
+ spin_unlock(&root->t_lock);
+ return he_new;
+ }
+ spin_unlock(&root->t_lock);
+
+ if (!alloc)
+ return ERR_PTR(-ENOENT);
+
+ he_new = kmem_cache_zalloc(hot_inode_item_cachep, GFP_NOFS);
+ if (!he_new)
+ return ERR_PTR(-ENOMEM);
+
+ hot_inode_item_init(he_new, root, ino);
+
+ goto redo;
+}
+EXPORT_SYMBOL_GPL(hot_inode_item_lookup);
+
+void hot_inode_item_delete(struct inode *inode)
+{
+ struct hot_info *root = inode->i_sb->s_hot_root;
+ struct hot_inode_item *he;
+
+ if (!root || !S_ISREG(inode->i_mode))
+ return;
+
+ he = hot_inode_item_lookup(root, inode->i_ino, 0);
+ if (IS_ERR(he))
+ return;
+
+ hot_comm_item_put(&he->hot_inode); /* for lookup */
+ hot_comm_item_unlink(root, &he->hot_inode);
+}
+EXPORT_SYMBOL_GPL(hot_inode_item_delete);
+
+/* he->i_lock is acquired in this function. */
+struct hot_range_item
+*hot_range_item_lookup(struct hot_inode_item *he, loff_t start, int alloc)
+{
+ struct rb_node **p;
+ struct rb_node *parent = NULL;
+ struct hot_comm_item *ci;
+ struct hot_range_item *hr, *hr_new = NULL;
+
+ start = hot_shift(start, RANGE_BITS, true);
+
+ /* walk tree to find insertion point */
+redo:
+ spin_lock(&he->i_lock);
+ p = &he->hot_range_tree.rb_node;
+ while (*p) {
+ parent = *p;
+ ci = rb_entry(parent, struct hot_comm_item, rb_node);
+ hr = container_of(ci, struct hot_range_item, hot_range);
+ if (start < hr->start)
+ p = &(*p)->rb_left;
+ else if (start > (hr->start + hr->len - 1))
+ p = &(*p)->rb_right;
+ else {
+ hot_comm_item_get(&hr->hot_range);
+ spin_unlock(&he->i_lock);
+ if(hr_new)
+ /*
+ * Lost the race. Somebody else inserted
+ * the item for the range. Free the
+ * newly allocated item.
+ */
+ kmem_cache_free(hot_range_item_cachep, hr_new);
+
+ if (test_bit(HOT_DELETING, &hr->hot_range.delete_flag))
+ return ERR_PTR(-ENOENT);
+
+ return hr;
+ }
+ }
+
+ if (hr_new) {
+ rb_link_node(&hr_new->hot_range.rb_node, parent, p);
+ rb_insert_color(&hr_new->hot_range.rb_node,
+ &he->hot_range_tree);
+ hot_comm_item_get(&hr_new->hot_range);
+ spin_unlock(&he->i_lock);
+ return hr_new;
+ }
+ spin_unlock(&he->i_lock);
+
+ if (!alloc)
+ return ERR_PTR(-ENOENT);
+
+ hr_new = kmem_cache_zalloc(hot_range_item_cachep, GFP_NOFS);
+ if (!hr_new)
+ return ERR_PTR(-ENOMEM);
+
+ hot_range_item_init(hr_new, he, start);
+
+ goto redo;
+}
+EXPORT_SYMBOL_GPL(hot_range_item_lookup);
+
+/*
+ * This function does the actual work of updating
+ * the frequency numbers.
+ *
+ * avg_delta_{reads,writes} are indeed a kind of simple moving
+ * average of the time difference between each of the last
+ * 2^(FREQ_POWER) reads/writes. If there have not yet been that
+ * many reads or writes, it's likely that the values will be very
+ * large; They are initialized to the largest possible value for the
+ * data type. Simply, we don't want a few fast access to a file to
+ * automatically make it appear very hot.
+ */
+static void hot_freq_calc(struct timespec old_atime,
+ struct timespec cur_time, u64 *avg)
+{
+ struct timespec delta_ts;
+ u64 new_delta;
+
+ delta_ts = timespec_sub(cur_time, old_atime);
+ new_delta = timespec_to_ns(&delta_ts) >> FREQ_POWER;
+
+ *avg = (*avg << FREQ_POWER) - *avg + new_delta;
+ *avg = *avg >> FREQ_POWER;
+}
+
+static void hot_freq_update(struct hot_info *root,
+ struct hot_comm_item *ci, bool write)
+{
+ struct timespec cur_time = current_kernel_time();
+ struct hot_freq_data *freq_data = &ci->hot_freq_data;
+
+ if (write) {
+ freq_data->nr_writes += 1;
+ hot_freq_calc(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;
+ hot_freq_calc(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.
*/
@@ -128,6 +363,55 @@ void __init hot_cache_init(void)
}
EXPORT_SYMBOL_GPL(hot_cache_init);

+/*
+ * Main function to update i/o access frequencies, and it will be called
+ * from read/writepages() hooks, which are read_pages(), do_writepages(),
+ * do_generic_file_read(), and __blockdev_direct_IO().
+ */
+void hot_update_freqs(struct inode *inode, loff_t start,
+ size_t len, int rw)
+{
+ struct hot_info *root = inode->i_sb->s_hot_root;
+ struct hot_inode_item *he;
+ struct hot_range_item *hr;
+ u64 range_size;
+ loff_t cur, end;
+
+ if (!root || (len == 0) || !S_ISREG(inode->i_mode))
+ return;
+
+ he = hot_inode_item_lookup(root, inode->i_ino, 1);
+ if (IS_ERR(he))
+ return;
+
+ hot_freq_update(root, &he->hot_inode, rw);
+
+ /*
+ * Align ranges on range size boundary
+ * to prevent proliferation of range structs
+ */
+ range_size = hot_shift(1, RANGE_BITS, true);
+ end = hot_shift((start + len + range_size - 1),
+ RANGE_BITS, false);
+ cur = hot_shift(start, RANGE_BITS, false);
+ for (; cur < end; cur++) {
+ hr = hot_range_item_lookup(he, cur, 1);
+ if (IS_ERR(hr)) {
+ WARN(1, "hot_range_item_lookup returns %ld\n",
+ PTR_ERR(hr));
+ hot_comm_item_put(&he->hot_inode);
+ return;
+ }
+
+ hot_freq_update(root, &hr->hot_range, rw);
+
+ hot_comm_item_put(&hr->hot_range);
+ }
+
+ hot_comm_item_put(&he->hot_inode);
+}
+EXPORT_SYMBOL_GPL(hot_update_freqs);
+
static struct hot_info *hot_tree_init(struct super_block *sb)
{
struct hot_info *root;
diff --git a/fs/hot_tracking.h b/fs/hot_tracking.h
index a2ee95f..bb4cb16 100644
--- a/fs/hot_tracking.h
+++ b/fs/hot_tracking.h
@@ -14,4 +14,8 @@

#include <linux/hot_tracking.h>

+/* size of sub-file ranges */
+#define RANGE_BITS 20
+#define FREQ_POWER 4
+
#endif /* __HOT_TRACKING__ */
diff --git a/fs/namei.c b/fs/namei.c
index 85e40d1..2eec542 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3394,6 +3394,8 @@ int vfs_unlink(struct inode *dir, struct dentry *dentry)
if (!dir->i_op->unlink)
return -EPERM;

+ hot_inode_item_delete(dentry->d_inode);
+
mutex_lock(&dentry->d_inode->i_mutex);
if (d_mountpoint(dentry))
error = -EBUSY;
diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
index fa99439..3c0cf57 100644
--- a/include/linux/hot_tracking.h
+++ b/include/linux/hot_tracking.h
@@ -67,6 +67,8 @@ struct hot_inode_item {
struct hot_comm_item hot_inode; /* node in hot_inode_tree */
struct rb_root hot_range_tree; /* tree of ranges */
spinlock_t i_lock; /* protect above tree */
+ struct hot_info *hot_root; /* associated hot_info */
+ u64 i_ino; /* inode number from inode */
};

/*
@@ -76,6 +78,9 @@ struct hot_inode_item {
struct hot_range_item {
struct hot_comm_item hot_range;
struct hot_inode_item *hot_inode; /* associated hot_inode_item */
+ loff_t start; /* offset in bytes */
+ size_t len; /* length in bytes */
+ int storage_type; /* type of storage */
};

struct hot_info {
@@ -89,6 +94,13 @@ extern void __init hot_cache_init(void);
extern int hot_track_init(struct super_block *sb);
extern void hot_track_exit(struct super_block *sb);
extern void hot_comm_item_put(struct hot_comm_item *ci);
+extern void hot_update_freqs(struct inode *inode, loff_t start,
+ size_t len, int rw);
+extern struct hot_inode_item *hot_inode_item_lookup(struct hot_info *root,
+ u64 ino, int alloc);
+extern struct hot_range_item *hot_range_item_lookup(struct hot_inode_item *he,
+ loff_t start, int alloc);
+extern void hot_inode_item_delete(struct inode *inode);

static inline u64 hot_shift(u64 counter, u32 bits, bool dir)
{
@@ -98,6 +110,11 @@ static inline u64 hot_shift(u64 counter, u32 bits, bool dir)
return counter >> bits;
}

+static inline void hot_comm_item_get(struct hot_comm_item *ci)
+{
+ kref_get(&ci->refs);
+}
+
#endif /* __KERNEL__ */

#endif /* _LINUX_HOTTRACK_H */
diff --git a/mm/filemap.c b/mm/filemap.c
index 7905fe7..eb64c49 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"

#define CREATE_TRACE_POINTS
@@ -1242,6 +1243,11 @@ readpage:
* PG_error will be set again if readpage fails.
*/
ClearPageError(page);
+
+ /* Hot data tracking */
+ hot_update_freqs(inode, (loff_t)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 4514ad7..4bbca3a 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -36,6 +36,7 @@
#include <linux/pagevec.h>
#include <linux/timer.h>
#include <linux/sched/rt.h>
+#include <linux/hot_tracking.h>
#include <trace/events/writeback.h>

/*
@@ -1921,13 +1922,24 @@ EXPORT_SYMBOL(generic_writepages);
int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
{
int ret;
+ loff_t start = 0;
+ size_t count = 0;

if (wbc->nr_to_write <= 0)
return 0;
+
+ start = mapping->writeback_index << PAGE_CACHE_SHIFT;
+ count = 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, start,
+ (count - wbc->nr_to_write) * PAGE_CACHE_SIZE, 1);
+
return ret;
}

diff --git a/mm/readahead.c b/mm/readahead.c
index daed28d..901396b 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
@@ -115,6 +116,11 @@ static int read_pages(struct address_space *mapping, struct file *filp,
unsigned page_idx;
int ret;

+ /* Hot data tracking */
+ hot_update_freqs(mapping->host,
+ list_to_page(pages)->index << PAGE_CACHE_SHIFT,
+ (size_t)nr_pages * PAGE_CACHE_SIZE, 0);
+
blk_start_plug(&plug);

if (mapping->a_ops->readpages) {
--
1.7.11.7

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