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SubjectRe: [RFC 00/11] VFS: hot data tracking
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hi, all maintainers.

ping? any comments are appreciated, thanks.

On Wed, Sep 12, 2012 at 10:31 PM, Zhi Yong Wu <zwu.kernel@gmail.com> wrote:
> Sorry, forgot CCed to Ted.
>
> On Tue, Sep 11, 2012 at 10:27 PM, <zwu.kernel@gmail.com> wrote:
>> From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
>>
>> HI, folks
>> I have pushed the patchset to my kernel dev git tree:
>> git@github.com:wuzhy/kernel.git
>>
>> Also, you can review it via
>> https://github.com/wuzhy/kernel/commits/hottrack
>>
>> NOTE:
>>
>> The patchset still has a lot of bugfix and cleanup to do. It is post
>> out mainly to make sure it is going in the correct direction and
>> hope to get some helpful comments from other guys.
>>
>> TODO List:
>>
>> 1.) Need to do scalability or performance tests.
>> 2.) Fix up bugs.
>> 3.) Strictly split this patchset to keep them in order
>> This patchset is in RFC state, i haven't strictly split it
>> When it is in PATCH state, i will strictly split it and let
>> them in order.
>> 4.) Turn some Micro in to tunables
>> TIME_TO_KICK, and HEAT_UPDATE_DELAY
>> 5.) Rafactor hot_hash_is_aging()
>> If you just made the timeout value a timespec and compared
>> the _timespecs_, you would be doing a lot fewer conversions.
>> 6.) Cleanup some unnecessary lock protect
>> 7.) Add more comments to explain how to calc temperature
>>
>> Ben Chociej, Matt Lupfer and Conor Scott originally wrote this code to
>> be very btrfs-specific. I've taken their code and attempted to
>> make it more generic and integrate it at the VFS level.
>>
>> INTRODUCTION:
>>
>> Essentially, this means maintaining some key stats
>> (like number of reads/writes, last read/write time, frequency of
>> reads/writes), then distilling those numbers down to a single
>> "temperature" value that reflects what data is "hot," and using that
>> temperature to move data to SSDs.
>>
>> The long-term goal of these patches is to allow some FSs,
>> e.g. Btrfs to intelligently utilize SSDs in a heterogenous volume.
>> Incidentally, this project has been motivated by
>> the Project Ideas page on the Btrfs wiki.
>>
>> Of course, users are warned not to run this code outside of development
>> environments. These patches are EXPERIMENTAL, and as such they might eat
>> your data and/or memory. That said, the code should be relatively safe
>> when the hottrack mount option are disabled.
>>
>> MOTIVATION:
>>
>> The overall goal of enabling hot data relocation to SSD has been
>> motivated by the Project Ideas page on the Btrfs wiki at
>> <https://btrfs.wiki.kernel.org/index.php/Project_ideas>.
>> It will divide into two steps. VFS provide hot data tracking function
>> while specific FS will provide hot data relocation function.
>> So as the first step of this goal, it is hoped that the patchset
>> for hot data tracking will eventually mature into VFS.
>>
>> This is essentially the traditional cache argument: SSD is fast and
>> expensive; HDD is cheap but slow. ZFS, for example, can already take
>> advantage of SSD caching. Btrfs should also be able to take advantage of
>> hybrid storage without many broad, sweeping changes to existing code.
>>
>> SUMMARY:
>>
>> - Hooks in existing vfs functions to track data access frequency
>>
>> - New rbtrees for tracking access frequency of inodes and sub-file
>> ranges (hot_rb.c)
>> The relationship between super_block and rbtree is as below:
>> super_block->s_hotinfo.hot_inode_tree
>> In include/linux/fs.h, one struct hot_info s_hotinfo is added to
>> super_block struct. Each FS instance can find hot tracking info
>> s_hotinfo via its super_block. In this hot_info, it store a lot of hot
>> tracking info such as hot_inode_tree, inode and range hash list, etc.
>>
>> - A hash list for indexing data by its temperature (hot_hash.c)
>>
>> - A debugfs interface for dumping data from the rbtrees (hot_debugfs.c)
>>
>> - A background kthread for updating inode heat info
>>
>> - Mount options for enabling temperature tracking(-o hottrack, default mean disabled)
>> (hot_track.c)
>>
>> - An ioctl to retrieve the frequency information collected for a certain
>> file
>>
>> - Ioctls to enable/disable frequency tracking per inode.
>>
>> Usage syntax:
>>
>> root@debian-i386:~# mount -o hottrack /dev/sdb /mnt
>> [ 1505.894078] device label test devid 1 transid 29 /dev/sdb
>> [ 1505.952977] btrfs: disk space caching is enabled
>> [ 1506.069678] vfs: turning on hot data tracking
>> root@debian-i386:~# mount -t debugfs none /sys/kernel/debug
>> root@debian-i386:~# ls -l /sys/kernel/debug/vfs_hotdata/
>> total 0
>> drwxr-xr-x 2 root root 0 Aug 8 04:40 sdb
>> root@debian-i386:~# ls -l /sys/kernel/debug/vfs_hotdata/sdb
>> total 0
>> -rw-r--r-- 1 root root 0 Aug 8 04:40 inode_data
>> -rw-r--r-- 1 root root 0 Aug 8 04:40 range_data
>> root@debian-i386:~# vi /mnt/file
>> root@debian-i386:~# cat /sys/kernel/debug/hot_track/sdb/inode_data
>> inode #279, reads 0, writes 1, avg read time 18446744073709551615,
>> avg write time 5251566408153596, temp 109
>> root@debian-i386:~# cat /sys/kernel/debug/hot_track/sdb/range_data
>> inode #279, range start 0 (range len 1048576) reads 0, writes 1,
>> avg read time 18446744073709551615, avg write time 1128690176623144209, temp 64
>> root@debian-i386:~# echo "hot data tracking test" >> /mnt/file
>> root@debian-i386:~# cat /sys/kernel/debug/hot_track/sdb/inode_data
>> inode #279, reads 0, writes 2, avg read time 18446744073709551615,
>> avg write time 4923343766042451, temp 109
>> root@debian-i386:~# cat /sys/kernel/debug/hot_track/sdb/range_data
>> inode #279, range start 0 (range len 1048576) reads 0, writes 2,
>> avg read time 18446744073709551615, avg write time 1058147040842596150, temp 64
>> root@debian-i386:~#
>>
>> Zhi Yong Wu (11):
>> vfs: introduce one structure hot_info
>> vfs: introduce one rb tree - hot_inode_tree
>> vfs: introduce 2 rb tree items - inode and range
>> vfs: add support for updating access frequency
>> vfs: add one new mount option -o hottrack
>> vfs: add init and exit support
>> vfs: introduce one hash table
>> vfs: enable hot data tracking
>> vfs: fork one private kthread to update temperature info
>> vfs: add 3 new ioctl interfaces
>> vfs: add debugfs support
>>
>> fs/Makefile | 3 +-
>> fs/compat_ioctl.c | 8 +
>> fs/dcache.c | 2 +
>> fs/direct-io.c | 10 +
>> fs/hot_debugfs.c | 488 ++++++++++++++++++++++++++++++++++
>> fs/hot_debugfs.h | 60 +++++
>> fs/hot_hash.c | 382 ++++++++++++++++++++++++++
>> fs/hot_hash.h | 112 ++++++++
>> fs/hot_rb.c | 648 +++++++++++++++++++++++++++++++++++++++++++++
>> fs/hot_rb.h | 81 ++++++
>> fs/hot_track.c | 85 ++++++
>> fs/hot_track.h | 23 ++
>> fs/ioctl.c | 132 +++++++++
>> fs/namespace.c | 10 +
>> fs/super.c | 11 +
>> include/linux/fs.h | 15 +
>> include/linux/hot_track.h | 169 ++++++++++++
>> mm/filemap.c | 8 +
>> mm/page-writeback.c | 21 ++
>> mm/readahead.c | 9 +
>> 20 files changed, 2276 insertions(+), 1 deletions(-)
>> create mode 100644 fs/hot_debugfs.c
>> create mode 100644 fs/hot_debugfs.h
>> create mode 100644 fs/hot_hash.c
>> create mode 100644 fs/hot_hash.h
>> create mode 100644 fs/hot_rb.c
>> create mode 100644 fs/hot_rb.h
>> create mode 100644 fs/hot_track.c
>> create mode 100644 fs/hot_track.h
>> create mode 100644 include/linux/hot_track.h
>>
>> --
>> 1.7.6.5
>>
>> --
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>
>
>
> --
> Regards,
>
> Zhi Yong Wu



--
Regards,

Zhi Yong Wu


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