The flex_bg inode allocator

[Xiang Wang <xiangw@google.com>]

Hi,

Recently I've found out that the flex_bg inode allocator(the
find_group_flex function called by ext4_new_inode) is actually not in
use unless we specify the "oldalloc" option on mount as well as
setting the flex_bg size to be > 1.
Currently, the default option on mount is "orlov".

We would like to know:
1) What's the current status of the flex_bg inode allocator? Will it
be set as a default soon?

2) If not, are there any particular reasons that it is held back? Is
it all because of the worse performance numbers shown in the two
metrics
("read tree total" and "read compiled tree total") in Compilebench?

3) Are there any ongoing efforts and/or future plans to improve it? Or
is there any work in similar directions?

Thanks,
Xiang