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Date: Wed, 7 Nov 2012 16:27:05 +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 03/19] vfs: add I/O frequency update function
On Wed, Nov 7, 2012 at 6:45 AM, Darrick J. Wong <darrick.wong@...cle.com> wrote:
> 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...
why?
>
>> + 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?
ah, good catch, thanks.
>
> Also, RANGE_SIZE means that the hot tracking range granularity is 1MiB? How
yes.
> did you decide on that? Will we ever want to change that?
It is one assumption, do you think 1 MB is not appropriate? Do you
mean to add one proc file interface for it?
>
>> + 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)); ?
OK, done.
>
> --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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--
Regards,
Zhi Yong Wu
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