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Date: Wed, 7 Nov 2012 10:58:02 -0800
From: "Darrick J. Wong" <darrick.wong@...cle.com>
To: Zhi Yong Wu <zwu.kernel@...il.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 07, 2012 at 04:34:35PM +0800, Zhi Yong Wu wrote:
> 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....
What kind of regressions are you afraid of, specifically? I don't think fstype
is performance-critical enough to worry about wreaking havoc in the caches due
to adding three function pointers.
> > 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).
I guess you could just require that everyone fill out .hot_temp_calc_fn,
even if they just point it to generic_hot_temp_calc.
--D
> >
> > --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
> >>
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
> >> the body of a message to majordomo@...r.kernel.org
> >> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>
>
> --
> Regards,
>
> Zhi Yong Wu
> --
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