[Ocfs2-devel] [PATCH 00/16] Ocfs2: Online defragmentaion V4.
Tristan Ye
tristan.ye at oracle.com
Thu Mar 17 23:35:27 PDT 2011
*. Let defrag handle partial extent moving
*. Incorporate Mark's comments.
*. Set several trivial constraints for threshold.
Rebased on 2.6.38:
http://oss.oracle.com/git/tye/ocfs2-tools.git/?p=tye/linux-2.6.git;a=shortlog;h=move_extents
-------------------------------------------------------------------------------
Changes since v2:
*. Add refcount support.
*. Share Copy-On-Writes codes with refcounttree.c
*. Re-organize the ordering of patches.
*. Fix several trivial bugs.
-------------------------------------------------------------------------------
Changes since v1:
*. implement following #2 strategy(simple extent_moving).
It's a quite rough patches series v2 for online defrag/ext_moving on OCFS2, it's
workable anyway, may look ugly though;) The essence of online file defragmentation is
extents moving like what btrfs and ext4 were doing, adding 'OCFS2_IOC_MOVE_EXT' ioctl
to ocfs2 allows two strategies upon defragmentation:
1. simple-defragmentation-in-kernl, which means kernel will be responsible for
claiming new clusters, and packing the defragmented extents according to a
user-specified threshold.
2. simple-extents moving, in this case, userspace play much more important role
when doing defragmentation, it needs to specify the new physical blk_offset
where extents will be moved, kernel itself will not do anything more than
moving the extents per requested, maybe kernel also needs to manage to
probe/validate the new_blkoffset to guarantee enough free space around there.
Above two operations using the same OCFS2_IOC_MOVE_EXT:
-------------------------------------------------------------------------------
#define OCFS2_MOVE_EXT_FL_AUTO_DEFRAG (0x00000001) /* Kernel manages to
claim new clusters
as the goal place
for extents moving */
#define OCFS2_MOVE_EXT_FL_COMPLETE (0x00000002) /* Move or defragmenation
completely gets done.
*/
struct ocfs2_move_extents {
/* All values are in bytes */
/* in */
__u64 me_start; /* Virtual start in the file to move */
__u64 me_len; /* Length of the extents to be moved */
__u64 me_goal; /* Physical offset of the goal */
__u64 me_thresh; /* Maximum distance from goal or threshold
for auto defragmentation */
__u64 me_flags; /* flags for the operation:
* - auto defragmentation.
* - refcount,xattr cases.
*/
/* out */
__u64 me_moved_len; /* moved length, are we completely done? */
__u64 me_new_offset; /* Resulting physical location */
__u32 me_reserved[2]; /* reserved for futhure */
};
-------------------------------------------------------------------------------
Following are some interesting data gathered from simple tests:
1. Performance improvement gained on I/O reads:
-------------------------------------------------------------------------------
* Before defragmentation *
[root at ocfs2-box4 ~]# sync
[root at ocfs2-box4 ~]# echo 3>/proc/sys/vm/drop_caches
[root at ocfs2-box4 ~]# time dd if=/storage/testfile-1 of=/dev/null
640000+0 records in
640000+0 records out
327680000 bytes (328 MB) copied, 19.9351 s, 16.4 MB/s
real 0m19.954s
user 0m0.246s
sys 0m1.111s
* Do defragmentation *
[root at ocfs2-box4 defrag]# ./defrag -s 0 -l 293601280 -t 3145728 /storage/testfile-1
* After defragmentation *
[root at ocfs2-box4 ~]# sync
[root at ocfs2-box4 ~]# echo 3>/proc/sys/vm/drop_caches
[root at ocfs2-box4 ~]# time dd if=/storage/testfile-1 of=/dev/null
640000+0 records in
640000+0 records out
327680000 bytes (328 MB) copied, 6.79885 s, 48.2 MB/s
real 0m6.969s
user 0m0.209s
sys 0m1.063s
-------------------------------------------------------------------------------
2. Extent tree layout via debugfs.ocfs2:
-------------------------------------------------------------------------------
* Before defragmentation *
Tree Depth: 1 Count: 243 Next Free Rec: 8
## Offset Clusters Block#
0 0 1173 86561
1 1173 1173 84527
2 2346 1151 81468
3 3497 1173 76362
4 4670 1173 74328
5 5843 1172 66150
6 7015 1460 70260
7 8475 662 87680
SubAlloc Bit: 1 SubAlloc Slot: 0
Blknum: 86561 Next Leaf: 84527
CRC32: abf06a6b ECC: 44bc
Tree Depth: 0 Count: 252 Next Free Rec: 252
## Offset Clusters Block# Flags
0 1 16 516104 0x0
1 17 1 554632 0x0
2 18 7 560144 0x0
3 25 1 565960 0x0
4 26 1 572632 0x
...
/* around 1700 extent records were hidden there */
...
138 9131 1 258968 0x0
139 9132 1 259568 0x0
140 9133 1 260168 0x0
141 9134 1 260768 0x0
142 9135 1 261368 0x0
143 9136 1 261968 0x0
* After defragmentation *
Tree Depth: 1 Count: 243 Next Free Rec: 1
## Offset Clusters Block#
0 0 9137 66081
SubAlloc Bit: 1 SubAlloc Slot: 0
Blknum: 66081 Next Leaf: 0
CRC32: 22897d34 ECC: 0619
Tree Depth: 0 Count: 252 Next Free Rec: 6
## Offset Clusters Block# Flags
0 1 1600 4412936 0x0
1 1601 1595 20669448 0x0
2 3196 1600 9358856 0x0
3 4796 1404 14516232 0x0
4 6200 1600 21627400 0x0
5 7800 1337 7483400 0x0
-------------------------------------------------------------------------------
TO-DO:
1. Adding refcount/xattr support.
2. Free space defragmentation.
Go to http://oss.oracle.com/osswiki/OCFS2/DesignDocs/OnlineDefrag for more details.
Tristan.
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