[Ocfs2-devel] [PATCH 0/9 v6] ocfs2: support append O_DIRECT write

[Junxiao Bi <junxiao.bi@oracle.com>]

On 01/20/2015 05:00 PM, Joseph Qi wrote:
> Hi Junxiao,
> 
> On 2015/1/20 16:26, Junxiao Bi wrote:
>> Hi Joseph,
>>
>> Did this version make any performance improvement with v5? I tested v5,
>> and it didn't improve performance with original buffer write + sync.
> No performance difference between these two versions.
> But we have tested with fio before, it shows about 5% performance
> improvement with normal buffer write (without sync).
> As I described, this feature is not truly for performance improvement.
> We aim to reduce the host page cache consumption. For example, dom0
> in virtualization case which won't be configured too much memory.
I cared the direct-io performance because recently i got a bug that
ocfs2 appending write direct-io performance was two times less than
ext4. Since you followed some idea from ext4, do you know why ext4 is
faster and any advise to improve ocfs2 performance?

Thanks,
Junxiao.
> 
> --
> Joseph
>>
>> Thanks,
>> Junxiao.
>>
>> On 01/20/2015 04:01 PM, Joseph Qi wrote:
>>> Currently in case of append O_DIRECT write (block not allocated yet),
>>> ocfs2 will fall back to buffered I/O. This has some disadvantages.
>>> Firstly, it is not the behavior as expected.
>>> Secondly, it will consume huge page cache, e.g. in mass backup scenario.
>>> Thirdly, modern filesystems such as ext4 support this feature.
>>>
>>> In this patch set, the direct I/O write doesn't fallback to buffer I/O
>>> write any more because the allocate blocks are enabled in direct I/O
>>> now.
>>>
>>> changelog:
>>> v6 <- v5:
>>> -- Take Mark's advice to use prefix "dio-" to distinguish dio orphan
>>>    entry from unlink/rename.
>>> -- Take Mark's advice to treat this feature as a ro compat feature.
>>> -- Fix a bug in case of not cluster aligned io, cluster_align should
>>>    be !zero_len, not !!zero_len.
>>> -- Fix a bug in case of fallocate with FALLOC_FL_KEEP_SIZE.
>>> -- Fix the wrong *ppos and written when completing the rest request
>>>    using buffer io.
>>>
>>> Corresponding ocfs2 tools (mkfs.ocfs2, tunefs.ocfs2, fsck.ocfs2, etc.)
>>> will be updated later.
>>>
>>>
>>> _______________________________________________
>>> Ocfs2-devel mailing list
>>> Ocfs2-devel at oss.oracle.com
>>> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
>>>
>>
>>
>>
> 
>