Patchwork [RFC,v2,01/10] vfs: introduce private rb structures

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Submitter Zhiyong Wu
Date Sept. 23, 2012, 12:56 p.m.
Message ID <1348404995-14372-2-git-send-email-zwu.kernel@gmail.com>
Download mbox | patch
Permalink /patch/186217/
State Not Applicable
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Comments

Zhiyong Wu - Sept. 23, 2012, 12:56 p.m.
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 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@linux.vnet.ibm.com>
---
 fs/Makefile                  |    2 +-
 fs/dcache.c                  |    2 +
 fs/hot_tracking.c            |  116 ++++++++++++++++++++++++++++++++++++++++++
 fs/hot_tracking.h            |   27 ++++++++++
 include/linux/fs.h           |    4 ++
 include/linux/hot_tracking.h |   96 ++++++++++++++++++++++++++++++++++
 6 files changed, 246 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
Dave Chinner - Sept. 25, 2012, 7:37 a.m.
On Sun, Sep 23, 2012 at 08:56:26PM +0800, zwu.kernel@gmail.com wrote:
> 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 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@linux.vnet.ibm.com>

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@linux.vnet.ibm.com>
> + *            Ben Chociej <bchociej@gmail.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/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.
Zhiyong Wu - Sept. 25, 2012, 7:57 a.m.
On Tue, Sep 25, 2012 at 3:37 PM, Dave Chinner <david@fromorbit.com> wrote:
> On Sun, Sep 23, 2012 at 08:56:26PM +0800, zwu.kernel@gmail.com wrote:
>> 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 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@linux.vnet.ibm.com>
>
> Just a coupl eof minor formatting things first up - I'll have more
> comments as I get deeper into the series.
All comments are very reasonable, and will be applied.
thanks for your review.

>
> ....
>> +/*
>> + * 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@linux.vnet.ibm.com>
>> + *            Ben Chociej <bchociej@gmail.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/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@fromorbit.com
Zhiyong Wu - Sept. 25, 2012, 8 a.m.
On Tue, Sep 25, 2012 at 3:37 PM, Dave Chinner <david@fromorbit.com> wrote:
> On Sun, Sep 23, 2012 at 08:56:26PM +0800, zwu.kernel@gmail.com wrote:
>> 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 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@linux.vnet.ibm.com>
>
> Just a coupl eof minor formatting things first up - I'll have more
> comments as I get deeper into the series.
OK, very look forward to seeing more on other patches, indeed thanks again.

>
> ....
>> +/*
>> + * 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@linux.vnet.ibm.com>
>> + *            Ben Chociej <bchociej@gmail.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/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@fromorbit.com
Ram Pai - Sept. 25, 2012, 10:20 a.m.
On Sun, Sep 23, 2012 at 08:56:26PM +0800, zwu.kernel@gmail.com wrote:
> 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 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@linux.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.

> +
> +/* 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.


RP

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Zhiyong Wu - Sept. 26, 2012, 3:20 a.m.
On Tue, Sep 25, 2012 at 6:20 PM, Ram Pai <linuxram@us.ibm.com> wrote:
> On Sun, Sep 23, 2012 at 08:56:26PM +0800, zwu.kernel@gmail.com wrote:
>> 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 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@linux.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
>

Patch

diff --git a/fs/Makefile b/fs/Makefile
index 2fb9779..9d29618 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 8086636..92470a1 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 "hot_tracking.h"
 #include "internal.h"
 #include "mount.h"
 
@@ -3164,6 +3165,7 @@  void __init vfs_caches_init(unsigned long mempages)
 	inode_init();
 	files_init(mempages);
 	mnt_init();
+	hot_track_cache_init();
 	bdev_cache_init();
 	chrdev_init();
 }
diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
new file mode 100644
index 0000000..173054b
--- /dev/null
+++ b/fs/hot_tracking.c
@@ -0,0 +1,116 @@ 
+/*
+ * fs/hot_tracking.c
+ *
+ * Copyright (C) 2012 IBM Corp. All rights reserved.
+ * Written by Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
+ *            Ben Chociej <bchociej@gmail.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 "hot_tracking.h"
+
+/* kmem_cache pointers for slab caches */
+static struct kmem_cache *hot_inode_item_cache;
+static struct kmem_cache *hot_range_item_cache;
+
+/*
+ * 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)
+{
+	tree->map = RB_ROOT;
+	rwlock_init(&tree->lock);
+}
+
+/*
+ * Initialize the hot range tree. Should be called for each new inode
+ * access or other user of the hot_range interface.
+ */
+void hot_rb_range_tree_init(struct hot_range_tree *tree)
+{
+	tree->map = RB_ROOT;
+	rwlock_init(&tree->lock);
+}
+
+/*
+ * 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)
+{
+	struct hot_inode_item *he = _item;
+
+	memset(he, 0, sizeof(*he));
+	kref_init(&he->refs);
+	spin_lock_init(&he->lock);
+	he->hot_freq_data.avg_delta_reads = (u64) -1;
+	he->hot_freq_data.avg_delta_writes = (u64) -1;
+	he->hot_freq_data.flags = FREQ_DATA_TYPE_INODE;
+	hot_rb_range_tree_init(&he->hot_range_tree);
+}
+
+/*
+ * 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_rb_range_item_init(void *_item)
+{
+	struct hot_range_item *hr = _item;
+
+	memset(hr, 0, sizeof(*hr));
+	kref_init(&hr->refs);
+	spin_lock_init(&hr->lock);
+	hr->hot_freq_data.avg_delta_reads = (u64) -1;
+	hr->hot_freq_data.avg_delta_writes = (u64) -1;
+	hr->hot_freq_data.flags = FREQ_DATA_TYPE_RANGE;
+}
+
+/* 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;
+}
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@linux.vnet.ibm.com>
+ *            Ben Chociej <bchociej@gmail.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/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)
+
+void __init hot_track_cache_init(void);
+
+#endif /* __HOT_TRACKING__ */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index aa11047..db1a144 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -415,6 +415,7 @@  struct inodes_stat_t {
 #include <linux/migrate_mode.h>
 #include <linux/uidgid.h>
 #include <linux/lockdep.h>
+#include <linux/hot_tracking.h>
 
 #include <asm/byteorder.h>
 
@@ -1578,6 +1579,9 @@  struct super_block {
 
 	/* Being remounted read-only */
 	int s_readonly_remount;
+
+	/* Hot data tracking info*/
+	struct hot_info s_hotinfo;
 };
 
 /* superblock cache pruning functions */
diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
new file mode 100644
index 0000000..a566f91
--- /dev/null
+++ b/include/linux/hot_tracking.h
@@ -0,0 +1,96 @@ 
+/*
+ *  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>
+ *            Ben Chociej <bchociej@gmail.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>
+
+/* 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;
+};
+
+/* 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;
+};
+
+struct hot_info {
+	/* red-black tree that keeps track of fs-wide hot data */
+	struct hot_inode_tree hot_inode_tree;
+};
+
+#endif  /* _LINUX_HOTTRACK_H */