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Date:	Wed, 7 Nov 2012 16:34:35 +0800
From:	Zhi Yong Wu <zwu.kernel@...il.com>
To:	"Darrick J. Wong" <darrick.wong@...cle.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	linuxram@...ux.vnet.ibm.com, viro@...iv.linux.org.uk,
	david@...morbit.com, tytso@....edu, cmm@...ibm.com,
	wuzhy@...ux.vnet.ibm.com, wenqing.lz@...bao.com
Subject: Re: [RFC v4+ hot_track 10/19] vfs: introduce hot func register framework

On Wed, Nov 7, 2012 at 7:30 AM, Darrick J. Wong <darrick.wong@...cle.com> wrote:
> On Mon, Oct 29, 2012 at 12:30:52PM +0800, zwu.kernel@...il.com wrote:
>> From: Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
>>
>>   Introduce one framwork to enable that specific FS
>> can register its own hot tracking functions.
>>
>> Signed-off-by: Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
>> ---
>>  fs/hot_tracking.c            |   78 ++++++++++++++++++++++++++++++++++++++----
>>  include/linux/hot_tracking.h |   25 +++++++++++++
>>  2 files changed, 96 insertions(+), 7 deletions(-)
>>
>> diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
>> index 0ef9cad..c6c6138 100644
>> --- a/fs/hot_tracking.c
>> +++ b/fs/hot_tracking.c
>> @@ -24,6 +24,9 @@
>>  #include <linux/limits.h>
>>  #include "hot_tracking.h"
>>
>> +static DEFINE_SPINLOCK(hot_func_list_lock);
>> +static LIST_HEAD(hot_func_list);
>> +
>>  /* kmem_cache pointers for slab caches */
>>  static struct kmem_cache *hot_inode_item_cachep __read_mostly;
>>  static struct kmem_cache *hot_range_item_cachep __read_mostly;
>> @@ -305,20 +308,23 @@ static u64 hot_average_update(struct timespec old_atime,
>>       return new_avg;
>>  }
>>
>> -static void hot_freq_data_update(struct hot_freq_data *freq_data, bool write)
>> +static void hot_freq_data_update(struct hot_info *root,
>> +             struct hot_freq_data *freq_data, bool write)
>>  {
>>       struct timespec cur_time = current_kernel_time();
>>
>>       if (write) {
>>               freq_data->nr_writes += 1;
>> -             freq_data->avg_delta_writes = hot_average_update(
>> +             freq_data->avg_delta_writes =
>> +                     root->hot_func_type->ops.hot_rw_freq_calc_fn(
>>                               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;
>> -             freq_data->avg_delta_reads = hot_average_update(
>> +             freq_data->avg_delta_reads =
>> +                     root->hot_func_type->ops.hot_rw_freq_calc_fn(
>>                               freq_data->last_read_time,
>>                               cur_time,
>>                               freq_data->avg_delta_reads);
>> @@ -430,7 +436,7 @@ static void hot_map_array_update(struct hot_freq_data *freq_data,
>>       struct hot_comm_item *comm_item;
>>       struct hot_inode_item *he;
>>       struct hot_range_item *hr;
>> -     u32 temp = hot_temp_calc(freq_data);
>> +     u32 temp = root->hot_func_type->ops.hot_temp_calc_fn(freq_data);
>>       u8 a_temp = temp >> (32 - HEAT_MAP_BITS);
>>       u8 b_temp = freq_data->last_temp >> (32 - HEAT_MAP_BITS);
>>
>> @@ -511,7 +517,7 @@ static void hot_range_update(struct hot_inode_item *he,
>>                               &hr_nodes[i]->hot_range.hot_freq_data, root);
>>
>>                       spin_lock(&hr_nodes[i]->hot_range.lock);
>> -                     obsolete = hot_is_obsolete(
>> +                     obsolete = root->hot_func_type->ops.hot_is_obsolete_fn(
>>                                       &hr_nodes[i]->hot_range.hot_freq_data);
>>                       spin_unlock(&hr_nodes[i]->hot_range.lock);
>>
>> @@ -668,7 +674,7 @@ void hot_update_freqs(struct inode *inode, u64 start,
>>       }
>>
>>       spin_lock(&he->hot_inode.lock);
>> -     hot_freq_data_update(&he->hot_inode.hot_freq_data, rw);
>> +     hot_freq_data_update(root, &he->hot_inode.hot_freq_data, rw);
>>       spin_unlock(&he->hot_inode.lock);
>>
>>       /*
>> @@ -685,7 +691,7 @@ void hot_update_freqs(struct inode *inode, u64 start,
>>               }
>>
>>               spin_lock(&hr->hot_range.lock);
>> -             hot_freq_data_update(&hr->hot_range.hot_freq_data, rw);
>> +             hot_freq_data_update(root, &hr->hot_range.hot_freq_data, rw);
>>               spin_unlock(&hr->hot_range.lock);
>>
>>               hot_range_item_put(hr);
>> @@ -695,6 +701,61 @@ void hot_update_freqs(struct inode *inode, u64 start,
>>  }
>>  EXPORT_SYMBOL_GPL(hot_update_freqs);
>>
>> +static struct hot_func_type hot_func_def = {
>> +     .hot_func_name = "hot_type_def",
>> +     .ops = {
>> +             .hot_rw_freq_calc_fn = hot_average_update,
>> +             .hot_temp_calc_fn    = hot_temp_calc,
>> +             .hot_is_obsolete_fn  = hot_is_obsolete,
>> +     },
>> +};
>
> If these hot_ops are per-filesystem, why not just embed a struct hot_func_ops
> inside of struct file_system_type?  That eliminates this _get function,
this _get function is very small, only some loc, if hot_func_ops is
embedded in struct file_system_type, i am afraid to introduce some
regressions....
> collision avoidance, etc.  You can fill in NULL function pointers in
fill in NULL func pointer? why?
> hot_track_init (or just code around them).
>
> --D
>
>> +
>> +static struct hot_func_type *hot_func_get(const char *name)
>> +{
>> +     struct hot_func_type *f, *h = &hot_func_def;
>> +
>> +     spin_lock(&hot_func_list_lock);
>> +     list_for_each_entry(f, &hot_func_list, list) {
>> +             if (!strcmp(f->hot_func_name, name))
>> +                     h = f;
>> +     }
>> +     spin_unlock(&hot_func_list_lock);
>> +
>> +     return h;
>> +}
>> +
>> +int hot_func_register(struct hot_func_type *h)
>> +{
>> +     struct hot_func_type *f, *t = NULL;
>> +
>> +     /* register, don't allow duplicate names */
>> +     spin_lock(&hot_func_list_lock);
>> +     list_for_each_entry(f, &hot_func_list, list) {
>> +             if (!strcmp(f->hot_func_name, h->hot_func_name))
>> +                     t = f;
>> +     }
>> +
>> +     if (t) {
>> +             spin_unlock(&hot_func_list_lock);
>> +             return -EBUSY;
>> +     }
>> +
>> +     list_add_tail(&h->list, &hot_func_list);
>> +     spin_unlock(&hot_func_list_lock);
>> +
>> +     return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(hot_func_register);
>> +
>> +void hot_func_unregister(struct hot_func_type *h)
>> +{
>> +     /* unregister */
>> +     spin_lock(&hot_func_list_lock);
>> +     list_del_init(&h->list);
>> +     spin_unlock(&hot_func_list_lock);
>> +}
>> +EXPORT_SYMBOL_GPL(hot_func_unregister);
>> +
>>  /*
>>   * Initialize the data structures for hot data tracking.
>>   */
>> @@ -714,6 +775,9 @@ int hot_track_init(struct super_block *sb)
>>       hot_inode_tree_init(root);
>>       hot_map_array_init(root);
>>
>> +     /* Get hot func type */
>> +     root->hot_func_type = hot_func_get(sb->s_type->name);
>> +
>>       root->update_wq = alloc_workqueue(
>>               "hot_update_wq", WQ_NON_REENTRANT, 0);
>>       if (!root->update_wq) {
>> diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
>> index 2ee0d02..3941052 100644
>> --- a/include/linux/hot_tracking.h
>> +++ b/include/linux/hot_tracking.h
>> @@ -23,6 +23,8 @@
>>  #define HEAT_MAP_BITS 8
>>  #define HEAT_MAP_SIZE (1 << HEAT_MAP_BITS)
>>
>> +#define HOT_NAME_MAX 16
>> +
>>  /*
>>   * A frequency data struct holds values that are used to
>>   * determine temperature of files and file ranges. These structs
>> @@ -73,6 +75,25 @@ struct hot_range_item {
>>       u32 len; /* length in bytes */
>>  };
>>
>> +typedef u64 (hot_rw_freq_calc_fn) (struct timespec old_atime,
>> +                     struct timespec cur_time, u64 old_avg);
>> +typedef u32 (hot_temp_calc_fn) (struct hot_freq_data *freq_data);
>> +typedef bool (hot_is_obsolete_fn) (struct hot_freq_data *freq_data);
>> +
>> +struct hot_func_ops {
>> +     hot_rw_freq_calc_fn *hot_rw_freq_calc_fn;
>> +     hot_temp_calc_fn *hot_temp_calc_fn;
>> +     hot_is_obsolete_fn *hot_is_obsolete_fn;
>> +};
>> +
>> +/* identifies an hot func type */
>> +struct hot_func_type {
>> +     char hot_func_name[HOT_NAME_MAX];
>> +     /* fields provided by specific FS */
>> +     struct hot_func_ops ops;
>> +     struct list_head list;
>> +};
>> +
>>  struct hot_info {
>>       struct radix_tree_root hot_inode_tree;
>>       spinlock_t lock; /*protect inode tree */
>> @@ -85,6 +106,7 @@ struct hot_info {
>>
>>       struct workqueue_struct *update_wq;
>>       struct delayed_work update_work;
>> +     struct hot_func_type *hot_func_type;
>>  };
>>
>>  extern void __init hot_cache_init(void);
>> @@ -93,4 +115,7 @@ extern void hot_track_exit(struct super_block *sb);
>>  extern void hot_update_freqs(struct inode *inode, u64 start,
>>                               u64 len, int rw);
>>
>> +extern int hot_func_register(struct hot_func_type *h);
>> +extern void hot_func_unregister(struct hot_func_type *h);
>> +
>>  #endif  /* _LINUX_HOTTRACK_H */
>> --
>> 1.7.6.5
>>
>> --
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-- 
Regards,

Zhi Yong Wu
--
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