Date:	Wed, 26 Sep 2012 11:20:27 +0800
From:	Zhi Yong Wu <zwu.kernel@...il.com>
To:	Ram Pai <linuxram@...ibm.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
	linuxram@...ux.vnet.ibm.com, viro@...iv.linux.org.uk,
	cmm@...ibm.com, tytso@....edu, marco.stornelli@...il.com,
	david@...morbit.com, stroetmann@...olinux.com, diegocg@...il.com,
	chris@...muel.org, Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
Subject: Re: [RFC v2 01/10] vfs: introduce private rb structures

On Tue, Sep 25, 2012 at 6:20 PM, Ram Pai <linuxram@...ibm.com> wrote:
> On Sun, Sep 23, 2012 at 08:56:26PM +0800, zwu.kernel@...il.com wrote:
>> From: Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
>>
>>   One root structure hot_info is defined, is hooked
>> up in super_block, and will be used to hold rb trees
>> root, hash list root and some other information, etc.
>>   Adds hot_inode_tree struct to keep track of
>> frequently accessed files, and be keyed by {inode, offset}.
>> Trees contain hot_inode_items representing those files
>> and ranges.
>>   Having these trees means that vfs can quickly determine the
>> temperature of some data by doing some calculations on the
>> hot_freq_data struct that hangs off of the tree item.
>>   Define two items hot_inode_item and hot_range_item,
>> one of them represents one tracked file
>> to keep track of its access frequency and the tree of
>> ranges in this file, while the latter represents
>> a file range of one inode.
>>   Each of the two structures contains a hot_freq_data
>> struct with its frequency of access metrics (number of
>> {reads, writes}, last {read,write} time, frequency of
>> {reads,writes}).
>>   Also, each hot_inode_item contains one hot_range_tree
>> struct which is keyed by {inode, offset, length}
>> and used to keep track of all the ranges in this file.
>>
>> Signed-off-by: Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
>> ---
>> +
> ..snip..
>
>> +/* A tree that sits on the hot_info */
>> +struct hot_inode_tree {
>> +     struct rb_root map;
>> +     rwlock_t lock;
>> +};
>> +
>> +/* A tree of ranges for each inode in the hot_inode_tree */
>> +struct hot_range_tree {
>> +     struct rb_root map;
>> +     rwlock_t lock;
>> +};
>
> Can as well have a generic datastructure called hot_tree instead
> of having two different datastructure which basically are the same.
OK.
>
>> +
>> +/* A frequency data struct holds values that are used to
>> + * determine temperature of files and file ranges. These structs
>> + * are members of hot_inode_item and hot_range_item
>> + */
>> +struct hot_freq_data {
>> +     struct timespec last_read_time;
>> +     struct timespec last_write_time;
>> +     u32 nr_reads;
>> +     u32 nr_writes;
>> +     u64 avg_delta_reads;
>> +     u64 avg_delta_writes;
>> +     u8 flags;
>> +     u32 last_temperature;
>> +};
>> +
>> +/* An item representing an inode and its access frequency */
>> +struct hot_inode_item {
>> +     /* node for hot_inode_tree rb_tree */
>> +     struct rb_node rb_node;
>> +     /* tree of ranges in this inode */
>> +     struct hot_range_tree hot_range_tree;
>> +     /* frequency data for this inode */
>> +     struct hot_freq_data hot_freq_data;
>> +     /* inode number, copied from inode */
>> +     unsigned long i_ino;
>> +     /* used to check for errors in ref counting */
>> +     u8 in_tree;
>> +     /* protects hot_freq_data, i_no, in_tree */
>> +     spinlock_t lock;
>> +     /* prevents kfree */
>> +     struct kref refs;
>> +};
>> +
>> +/*
>> + * An item representing a range inside of an inode whose frequency
>> + * is being tracked
>> + */
>> +struct hot_range_item {
>> +     /* node for hot_range_tree rb_tree */
>> +     struct rb_node rb_node;
>> +     /* frequency data for this range */
>> +     struct hot_freq_data hot_freq_data;
>> +     /* the hot_inode_item associated with this hot_range_item */
>> +     struct hot_inode_item *hot_inode;
>> +     /* starting offset of this range */
>> +     u64 start;
>> +     /* length of this range */
>> +     u64 len;
>> +     /* used to check for errors in ref counting */
>> +     u8 in_tree;
>> +     /* protects hot_freq_data, start, len, and in_tree */
>> +     spinlock_t lock;
>> +     /* prevents kfree */
>> +     struct kref refs;
>> +};
>
> might as well have just one generic datastructure called hot_item with
> all the common fields and then have
>
>         struct hot_inode_item  {
>                 struct hot_item hot_inode;
>                 struct hot_tree hot_range_tree;
>                 unsigned long i_ino;
>         }
>
>         and
>
>         struct hot_range_item {
>                 struct hot_item hot_range;
>                 u64 start;
>                 u64 len;        /* length of this range */
>         }
>
> This should help you eliminate some duplicate code as well.
OK, i will try to apply them. thanks.
>
>
> RP
>



-- 
Regards,

Zhi Yong Wu
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