On Sun, Sep 23, 2012 at 08:56:26PM +0800, zwu.kernel@xxxxxxxxx wrote:
> From: Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxxxxx>
Just a coupl eof minor formatting things first up - I'll have more
comments as I get deeper into the series.
....
> +/*
> + * Initialize the inode tree. Should be called for each new inode
> + * access or other user of the hot_inode interface.
> + */
> +static void hot_rb_inode_tree_init(struct hot_inode_tree *tree)
The names of these are a bit clunky. You probably don't need the
"_rb_" in the function name. i.e. hot_inode_tree_init() is
sufficient, and if we every want to change in the tree type we don't
have to rename every single function...
.....
> +/*
> + * Initialize a new hot_inode_item structure. The new structure is
> + * returned with a reference count of one and needs to be
> + * freed using free_inode_item()
> + */
> +void hot_rb_inode_item_init(void *_item)
> +{
The usual naming convention for slab initialiser functions is to use
a suffix of "_once" to indicate it is only ever called once per
slab object instantiation, not every time the object is allocated
fom the slab. See, for example, inode_init_once() and
inode_init_always().
so, that would make this function hot_inode_item_init_once().
....
> +/* init hot_inode_item and hot_range_item kmem cache */
> +static int __init hot_rb_item_cache_init(void)
> +{
> + hot_inode_item_cache = kmem_cache_create("hot_inode_item",
> + sizeof(struct hot_inode_item), 0,
> + SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
> + hot_rb_inode_item_init);
> + if (!hot_inode_item_cache)
> + goto inode_err;
> +
> + hot_range_item_cache = kmem_cache_create("hot_range_item",
> + sizeof(struct hot_range_item), 0,
> + SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
> + hot_rb_range_item_init);
> + if (!hot_range_item_cache)
> + goto range_err;
> +
> + return 0;
> +
> +range_err:
> + kmem_cache_destroy(hot_inode_item_cache);
> +inode_err:
> + return -ENOMEM;
> +}
> +
> +/*
> + * Initialize kmem cache for hot_inode_item
> + * and hot_range_item
> + */
> +void __init hot_track_cache_init(void)
> +{
> + if (hot_rb_item_cache_init())
> + return;
No real need to have a hot_rb_item_cache_init() function here - just
open code it all in the hot_track_cache_init() function.
> +}
> diff --git a/fs/hot_tracking.h b/fs/hot_tracking.h
> new file mode 100644
> index 0000000..269b67a
> --- /dev/null
> +++ b/fs/hot_tracking.h
> @@ -0,0 +1,27 @@
> +/*
> + * fs/hot_tracking.h
> + *
> + * Copyright (C) 2012 IBM Corp. All rights reserved.
> + * Written by Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx>
> + * Ben Chociej <bchociej@xxxxxxxxx>
> + *
> + * 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/rbtree.h>
> +#include <linux/hot_tracking.h>
> +
> +/* values for hot_freq_data flags */
> +/* freq data struct is for an inode */
> +#define FREQ_DATA_TYPE_INODE (1 << 0)
> +/* freq data struct is for a range */
> +#define FREQ_DATA_TYPE_RANGE (1 << 1)
The comments are redundant - the name of the object documents it's
use sufficiently. ie.
/* values for hot_freq_data flags */
#define FREQ_DATA_TYPE_INODE (1 << 0)
#define FREQ_DATA_TYPE_RANGE (1 << 1)
is just fine by itself.
....
> +/* 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
> + */
/*
* This is a
* multiline comment. ;)
*/
> +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;
may as well make the flags a u32 - the compiler will ues that much
space anyway as it aligned the u32 last_temperature variable after
it.
> +};
> +
> +/* 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;
It's hard to see the code in the commentsi, and some of comments are
redundant.. It's easier to read if you do this:
struct hot_inode_item {
struct rb_node node; /* hot_inode_tree index */
struct hot_range_tree hot_range_tree; /* tree of ranges */
struct hot_freq_data hot_freq_data; /* frequency data */
unsigned long i_ino; /* inode number from inode */
u8 in_tree; /* ref counting check */
spinlock_t lock; /* protects object data */
struct kref refs; /* prevents kfree */
}
Also:
- i_ino really needs to be a 64 bit quantity as some
filesystems can use 64 bit inode numbers even on 32
bit systems (e.g. XFS).
- in_tree can be u32 or a flags field if it is boolean. if
it is just debug, then maybe it can be removed whenteh
code is ready for commit.
> +};
> +
> +/*
> + * 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;
What units?
u64 start; /* start offset in bytes */
u64 len /* length in bytes */
> + /* 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;
> +};
> +
> +struct hot_info {
> + /* red-black tree that keeps track of fs-wide hot data */
> + struct hot_inode_tree hot_inode_tree;
> +};
The comment is redundant...
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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