On Tue, Oct 30, 2012 at 6:04 AM, ching [off-list ref] wrote:

Hi all,

I am testing my btrfs root partition with "max_inline=0", and 64k leaf size for weeks and it seems that it is fine.


AFAIK btrfs inline small files into metadata by default, I am curious why?

If there is only a few small files, then there will be neither effect nor benefit at all
If there is a lot of small files, then the size of metadata will be undesirable due to deduplication

there are also some email threads related to problem of metadata inline (i don't know whether they are fixed in recent kernel):
http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg16295.html
http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg05265.html

How about turning off inline so that btrfs works better "out of the box"?

ching

I did some rough benchmarking around this a few weeks ago.  I'll try
to clean up my method and post the results.

I was working with multiple copies and rsyncs of kernel sources, which
have many candidate files for inlining.

To my surprise, my btrfs benchmarks were always the same or faster
when I let btrfs inline the files, even though metadata was much
larger.