[Ocfs2-devel] [PATCH 0/7] ocfs2: allocate blocks in direct I/O write

[Joseph Qi]

Hi Andrew,
Currently in case of O_DIRECT append 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.
So please consider, thanks.

On 2014/9/11 3:42, Andrew Morton wrote:
> On Wed, 10 Sep 2014 20:38:04 +0800 WeiWei Wang <wangww631 at huawei.com> wrote:
> 
>> hi all,
>> In ocfs2 append I/O write and fill holes I/O write situation, blocks have not been allocated yet, so the direct I/O write will fallback to buffer I/O write.
>> Buffer I/O write the data to page cache first, then flush the page cache to disk, this will consume some performance. In this patch, the direct I/O write
>> doesn't not need to fallback to buffer I/O write any more because the allocate blocks are enabled in direct I/O now.
>>
> 
> The entire point of the patchset is to improve performance, but the
> changelog contains no performance measurements!  How do we know it's
> worth considering?  Please include quantitative benchmarking results
> in the changelog.
> 
> 
> 
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