Re: [RFC v2 05/10] vfs: introduce one hash table
From: Ram Pai <hidden>
Date: 2012-09-25 09:54:01
Also in:
linux-ext4, linux-fsdevel, lkml
On Sun, Sep 23, 2012 at 08:56:30PM +0800, zwu.kernel@gmail.com wrote:
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From: Zhi Yong Wu <redacted> Adds a hash table structure which contains a lot of hash list and is used to efficiently look up the data temperature of a file or its ranges. In each hash list of hash table, the hash node will keep track of temperature info. Signed-off-by: Zhi Yong Wu <redacted> --- fs/hot_tracking.c | 77 ++++++++++++++++++++++++++++++++++++++++- include/linux/hot_tracking.h | 35 +++++++++++++++++++ 2 files changed, 110 insertions(+), 2 deletions(-)diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c index fa89f70..5f96442 100644 --- a/fs/hot_tracking.c +++ b/fs/hot_tracking.c@@ -16,6 +16,7 @@ #include <linux/module.h> #include <linux/spinlock.h> #include <linux/hardirq.h> +#include <linux/hash.h> #include <linux/fs.h> #include <linux/blkdev.h> #include <linux/types.h>@@ -24,6 +25,9 @@
...snip...
+/* Hash list heads for hot hash table */
+struct hot_hash_head {
+ struct hlist_head hashhead;
+ rwlock_t rwlock;
+ u32 temperature;
+};
+
+/* Nodes stored in each hash list of hash table */
+struct hot_hash_node {
+ struct hlist_node hashnode;
+ struct list_head node;
+ struct hot_freq_data *hot_freq_data;
+ struct hot_hash_head *hlist;
+ spinlock_t lock; /* protects hlist */
+
+ /*
+ * number of references to this node
+ * equals 1 (hashlist entry)
+ */
+ struct kref refs;
+};Dont see why you need yet another datastructure to hash the inode_item and the range_item into a hash list. You can just add another hlist_node in the inode_item and range_item. This field can be then used to link into the corresponding hash list. You can use the container_of() get to the inode_item or the range_item using the hlist_node field. You can thus eliminate a lot of code.
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+ /* An item representing an inode and its access frequency */ struct hot_inode_item { /* node for hot_inode_tree rb_tree */@@ -68,6 +93,8 @@ struct hot_inode_item { spinlock_t lock; /* prevents kfree */ struct kref refs; + /* hashlist node for this inode */ + struct hot_hash_node *heat_node;
this can be just struct hlist_node head_node; /* lookup hot_inode hash list */ Use this field to link it into the corresponding hashlist.
};
this can be just
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/*@@ -91,6 +118,8 @@ struct hot_range_item { spinlock_t lock; /* prevents kfree */ struct kref refs; + /* hashlist node for this range */ + struct hot_hash_node *heat_node;
this can be just struct hlist_node head_node; /* lookup hot_range hash list */
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}; struct hot_info {@@ -98,6 +127,12 @@ struct hot_info { /* red-black tree that keeps track of fs-wide hot data */ struct hot_inode_tree hot_inode_tree; + + /* hash map of inode temperature */ + struct hot_hash_head heat_inode_hl[HEAT_HASH_SIZE]; + + /* hash map of range temperature */ + struct hot_hash_head heat_range_hl[HEAT_HASH_SIZE]; }; #endif /* _LINUX_HOTTRACK_H */