From: Zhi Yong Wu Subject: Re: [RFC v4+ hot_track 03/19] vfs: add I/O frequency update function Date: Thu, 8 Nov 2012 10:52:51 +0800 Message-ID: References: <1351485061-12297-1-git-send-email-zwu.kernel@gmail.com> <1351485061-12297-4-git-send-email-zwu.kernel@gmail.com> <20121106224539.GB4255@blackbox.djwong.org> <20121107184952.GA4143@blackbox.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, linuxram@linux.vnet.ibm.com, viro@zeniv.linux.org.uk, david@fromorbit.com, tytso@mit.edu, cmm@us.ibm.com, wuzhy@linux.vnet.ibm.com, wenqing.lz@taobao.com To: "Darrick J. Wong" Return-path: Received: from mail-bk0-f46.google.com ([209.85.214.46]:47915 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752549Ab2KHCwx (ORCPT ); Wed, 7 Nov 2012 21:52:53 -0500 In-Reply-To: <20121107184952.GA4143@blackbox.djwong.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, Nov 8, 2012 at 2:49 AM, Darrick J. Wong wrote: > On Wed, Nov 07, 2012 at 04:27:05PM +0800, Zhi Yong Wu wrote: >> On Wed, Nov 7, 2012 at 6:45 AM, Darrick J. Wong wrote: >> > On Mon, Oct 29, 2012 at 12:30:45PM +0800, zwu.kernel@gmail.com wrote: >> >> From: Zhi Yong Wu >> >> >> >> Add some util helpers to update access frequencies >> >> for one file or its range. >> >> >> >> Signed-off-by: Zhi Yong Wu >> >> --- >> >> 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->avg_delta_{reads,writes} seems to be an in/out parameter, but by > specifying it once as an in parameter and again as an lvalue, you're increasing > the chances that someone will screw it up some time later -- you're not > preventing me from accidentally writing this: > > freq_data->avg_delta_writes = hot_average_update(..., freq_data->avg_delta_reads); > > ...which (at least in my head) becomes an easier mistake to make once you start > mixing in the function pointers a few patches later, and (my) brain has to wrap > itself around all the punctuation. > >> >> + 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. > > Actually, I should go further -- why not use loff_t? The rest of the fs/ code > does. done, 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? > > I don't know about a procfs interface -- debugfs, perhaps? > > But actually, I was thinking that the fs might have a better idea of the range > granularity that it wants to handle. Possibly it might be useful to try to > align with raid stripes or other topology, too... though that's difficult. > > Also, for the fses that use allocation units (clusters), it might be useful > to collect heat data per-cluster. > > On the other hand, it might not make much of a difference since most files tend > to fit in ~4K anyway, and the extra granularity will increase memory > consumption for large files. I don't mind having a 1MB default, but having a > knob would certainly make it easier to tune, or in the future, to test if that > 1MB default still makes sense. thanks. > > --D > >> > >> >> + 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 >> >> >> >> -- >> >> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in >> >> the body of a message to majordomo@vger.kernel.org >> >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> >> >> -- >> Regards, >> >> Zhi Yong Wu >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- Regards, Zhi Yong Wu