Re: [PATCH 00/11 v2] Btrfs: improve write ahead log with sub transaction

[liubo <liubo2009@cn.fujitsu.com>]

This includes the two patches that we've discussed before.

I sent this as a whole just in case you have to patch the code by yourself. :)

thanks,
liubo

On 05/26/2011 04:19 PM, Liu Bo wrote:
> I've been working to try to improve the write-ahead log's performance,
> and I found that the bottleneck addresses in the checksum items,
> especially when we want to make a random write on a large file, e.g a 4G file.
> 
> Then a idea for this suggested by Chris is to use sub transaction ids and just
> to log the part of inode that had changed since either the last log commit or
> the last transaction commit.  And as we also push the sub transid into the btree
> blocks, we'll get much faster tree walks.  As a result, we abandon the original
> brute force approach, which is "to delete all items of the inode in log",
> to making sure we get the most uptodate copies of everything, and instead
> we manage to "find and merge", i.e. finding extents in the log tree and merging
> in the new extents from the file.
> 
> This patchset puts the above idea into code, and although the code is now more
> complex, it brings us a great deal of performance improvement.
> 
> Beside the improvement of log, patch 8 fixes a small but critical bug of log code
> with sub transaction.
> 
> Here I have some test results to show, I use sysbench to do "random write + fsync".
> 
> ===
> sysbench --test=fileio --num-threads=1 --file-num=2 --file-block-size=4K --file-total-size=8G --file-test-mode=rndwr --file-io-mode=sync --file-extra-flags=  [prepare, run]
> ===
> 
> Sysbench args:
>   - Number of threads: 1
>   - Extra file open flags: 0
>   - 2 files, 4Gb each
>   - Block size 4Kb
>   - Number of random requests for random IO: 10000
>   - Read/Write ratio for combined random IO test: 1.50
>   - Periodic FSYNC enabled, calling fsync() each 100 requests.
>   - Calling fsync() at the end of test, Enabled.
>   - Using synchronous I/O mode
>   - Doing random write test
> 
> Sysbench results:
> ===
>    Operations performed:  0 Read, 10000 Write, 200 Other = 10200 Total
>    Read 0b  Written 39.062Mb  Total transferred 39.062Mb
> ===
> a) without patch:  (*SPEED* : 451.01Kb/sec)
>    112.75 Requests/sec executed
> 
> b) with patch:     (*SPEED* : 4.3621Mb/sec)
>    1116.71 Requests/sec executed
> 
> v1->v2: fix a EEXIST by logged_trans and a mismatch by log root generation
> 
> Liu Bo (11):
>   Btrfs: introduce sub transaction stuff
>   Btrfs: update block generation if should_cow_block fails
>   Btrfs: modify btrfs_drop_extents API
>   Btrfs: introduce first sub trans
>   Btrfs: still update inode trans stuff when size remains unchanged
>   Btrfs: improve log with sub transaction
>   Btrfs: add checksum check for log
>   Btrfs: fix a bug of log check
>   Btrfs: kick off useless code
>   Btrfs: deal with EEXIST after iput
>   Btrfs: use the right generation number to read log_root_tree
> 
>  fs/btrfs/btrfs_inode.h |   12 ++-
>  fs/btrfs/ctree.c       |   69 +++++++++----
>  fs/btrfs/ctree.h       |    5 +-
>  fs/btrfs/disk-io.c     |   12 +-
>  fs/btrfs/extent-tree.c |   10 +-
>  fs/btrfs/file.c        |   22 ++---
>  fs/btrfs/inode.c       |   33 ++++---
>  fs/btrfs/ioctl.c       |    6 +-
>  fs/btrfs/relocation.c  |    6 +-
>  fs/btrfs/transaction.c |   13 ++-
>  fs/btrfs/transaction.h |   19 +++-
>  fs/btrfs/tree-defrag.c |    2 +-
>  fs/btrfs/tree-log.c    |  267 +++++++++++++++++++++++++++++++++++-------------
>  13 files changed, 330 insertions(+), 146 deletions(-)
> 
>