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Date: Tue, 6 Nov 2012 14:45:39 -0800
From: "Darrick J. Wong" <darrick.wong@...cle.com>
To: 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 03/19] vfs: add I/O frequency update function
On Mon, Oct 29, 2012 at 12:30:45PM +0800, zwu.kernel@...il.com wrote:
> From: Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
>
> Add some util helpers to update access frequencies
> for one file or its range.
>
> Signed-off-by: Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
> ---
> fs/hot_tracking.c | 179 ++++++++++++++++++++++++++++++++++++++++++
> fs/hot_tracking.h | 7 ++
> include/linux/hot_tracking.h | 2 +
> 3 files changed, 188 insertions(+), 0 deletions(-)
>
> diff --git a/fs/hot_tracking.c b/fs/hot_tracking.c
> index 68591f0..0a7d9a3 100644
> --- a/fs/hot_tracking.c
> +++ b/fs/hot_tracking.c
> @@ -172,6 +172,137 @@ static void hot_inode_tree_exit(struct hot_info *root)
> }
> }
>
> +struct hot_inode_item
> +*hot_inode_item_find(struct hot_info *root, u64 ino)
> +{
> + struct hot_inode_item *he;
> + int ret;
> +
> +again:
> + spin_lock(&root->lock);
> + he = radix_tree_lookup(&root->hot_inode_tree, ino);
> + if (he) {
> + kref_get(&he->hot_inode.refs);
> + spin_unlock(&root->lock);
> + return he;
> + }
> + spin_unlock(&root->lock);
> +
> + he = kmem_cache_zalloc(hot_inode_item_cachep,
> + GFP_KERNEL | GFP_NOFS);
> + if (!he)
> + return ERR_PTR(-ENOMEM);
> +
> + hot_inode_item_init(he, ino, &root->hot_inode_tree);
> +
> + ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
> + if (ret) {
> + kmem_cache_free(hot_inode_item_cachep, he);
> + return ERR_PTR(ret);
> + }
> +
> + spin_lock(&root->lock);
> + ret = radix_tree_insert(&root->hot_inode_tree, ino, he);
> + if (ret == -EEXIST) {
> + kmem_cache_free(hot_inode_item_cachep, he);
> + spin_unlock(&root->lock);
> + radix_tree_preload_end();
> + goto again;
> + }
> + spin_unlock(&root->lock);
> + radix_tree_preload_end();
> +
> + kref_get(&he->hot_inode.refs);
> + return he;
> +}
> +EXPORT_SYMBOL_GPL(hot_inode_item_find);
> +
> +static struct hot_range_item
> +*hot_range_item_find(struct hot_inode_item *he,
> + u32 start)
> +{
> + struct hot_range_item *hr;
> + int ret;
> +
> +again:
> + spin_lock(&he->lock);
> + hr = radix_tree_lookup(&he->hot_range_tree, start);
> + if (hr) {
> + kref_get(&hr->hot_range.refs);
> + spin_unlock(&he->lock);
> + return hr;
> + }
> + spin_unlock(&he->lock);
> +
> + hr = kmem_cache_zalloc(hot_range_item_cachep,
> + GFP_KERNEL | GFP_NOFS);
> + if (!hr)
> + return ERR_PTR(-ENOMEM);
> +
> + hot_range_item_init(hr, start, he);
> +
> + ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
> + if (ret) {
> + kmem_cache_free(hot_range_item_cachep, hr);
> + return ERR_PTR(ret);
> + }
> +
> + spin_lock(&he->lock);
> + ret = radix_tree_insert(&he->hot_range_tree, start, hr);
> + if (ret == -EEXIST) {
> + kmem_cache_free(hot_range_item_cachep, hr);
> + spin_unlock(&he->lock);
> + radix_tree_preload_end();
> + goto again;
> + }
> + spin_unlock(&he->lock);
> + radix_tree_preload_end();
> +
> + kref_get(&hr->hot_range.refs);
> + return hr;
> +}
> +
> +/*
> + * This function does the actual work of updating
> + * the frequency numbers, whatever they turn out to be.
> + */
> +static u64 hot_average_update(struct timespec old_atime,
> + struct timespec cur_time, u64 old_avg)
> +{
> + struct timespec delta_ts;
> + u64 new_avg;
> + u64 new_delta;
> +
> + delta_ts = timespec_sub(cur_time, old_atime);
> + new_delta = timespec_to_ns(&delta_ts) >> FREQ_POWER;
> +
> + new_avg = (old_avg << FREQ_POWER) - old_avg + new_delta;
> + new_avg = new_avg >> FREQ_POWER;
> +
> + return new_avg;
> +}
> +
> +static void hot_freq_data_update(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->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->last_read_time,
> + cur_time,
> + freq_data->avg_delta_reads);
I think you could just pass in a pointer to
freq_data->avg_delta_{writes,reads} here...
> + freq_data->last_read_time = cur_time;
> + }
> +}
> +
> /*
> * Initialize kmem cache for hot_inode_item and hot_range_item.
> */
> @@ -199,6 +330,54 @@ err:
> EXPORT_SYMBOL_GPL(hot_cache_init);
>
> /*
> + * Main function to update access frequency from read/writepage(s) hooks
> + */
> +void hot_update_freqs(struct inode *inode, u64 start,
> + u64 len, int rw)
> +{
> + struct hot_info *root = inode->i_sb->s_hot_root;
> + struct hot_inode_item *he;
> + struct hot_range_item *hr;
> + u32 cur, end;
> +
> + if (!root || (len == 0))
> + return;
> +
> + he = hot_inode_item_find(root, inode->i_ino);
> + if (IS_ERR(he)) {
> + WARN_ON(1);
> + return;
> + }
> +
> + spin_lock(&he->hot_inode.lock);
> + hot_freq_data_update(&he->hot_inode.hot_freq_data, rw);
> + spin_unlock(&he->hot_inode.lock);
> +
> + /*
> + * Align ranges on RANGE_SIZE boundary
> + * to prevent proliferation of range structs
> + */
> + end = (start + len + RANGE_SIZE - 1) >> RANGE_BITS;
> + for (cur = (start >> RANGE_BITS); cur < end; cur++) {
Hm... start is u64, cur is u32, RANGE_BITS is 20. Doesn't this overflow if,
say, I have a sparse file with blocks way out at 2^53 bytes?
Also, RANGE_SIZE means that the hot tracking range granularity is 1MiB? How
did you decide on that? Will we ever want to change that?
> + hr = hot_range_item_find(he, cur);
> + if (IS_ERR(hr)) {
> + WARN_ON(1);
WARN(1, "hot_range_item_find returns %d\n", PTR_ERR(hr)); ?
--D
> + hot_inode_item_put(he);
> + return;
> + }
> +
> + spin_lock(&hr->hot_range.lock);
> + hot_freq_data_update(&hr->hot_range.hot_freq_data, rw);
> + spin_unlock(&hr->hot_range.lock);
> +
> + hot_range_item_put(hr);
> + }
> +
> + hot_inode_item_put(he);
> +}
> +EXPORT_SYMBOL_GPL(hot_update_freqs);
> +
> +/*
> * Initialize the data structures for hot data tracking.
> */
> int hot_track_init(struct super_block *sb)
> diff --git a/fs/hot_tracking.h b/fs/hot_tracking.h
> index e7ba121..cc4666e 100644
> --- a/fs/hot_tracking.h
> +++ b/fs/hot_tracking.h
> @@ -20,6 +20,13 @@
> #define FREQ_DATA_TYPE_INODE (1 << 0)
> #define FREQ_DATA_TYPE_RANGE (1 << 1)
>
> +/* size of sub-file ranges */
> +#define RANGE_BITS 20
> +#define RANGE_SIZE (1 << RANGE_BITS)
> +
> +#define FREQ_POWER 4
> +
> void hot_inode_item_put(struct hot_inode_item *he);
> +struct hot_inode_item *hot_inode_item_find(struct hot_info *root, u64 ino);
>
> #endif /* __HOT_TRACKING__ */
> diff --git a/include/linux/hot_tracking.h b/include/linux/hot_tracking.h
> index 4233207..e2d6028 100644
> --- a/include/linux/hot_tracking.h
> +++ b/include/linux/hot_tracking.h
> @@ -71,5 +71,7 @@ struct hot_info {
> extern void __init hot_cache_init(void);
> extern int hot_track_init(struct super_block *sb);
> extern void hot_track_exit(struct super_block *sb);
> +extern void hot_update_freqs(struct inode *inode, u64 start,
> + u64 len, int rw);
>
> #endif /* _LINUX_HOTTRACK_H */
> --
> 1.7.6.5
>
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