Re: HAMMER changes in HEAD, also needs testing

[Michael Neumann <mneumann@xxxxxxxx>]

Matthew Dillon schrieb:
>     I've made some fairly straightforward changes to HAMMER in HEAD, but
>     they need testing.
>
>     * Inode numbers are now allocated to maintain linearity with the
>       directory scan order, when possible.  Note however that this
>       optimization breaks if a file is created under a temporary name
>       and then renamed.
>
>       This should significantly improve cpdup, tar, cpio, ls, and find.
>       The optimization only applies to newly created directory trees,
>       existing trees cannot be reoptimized since their inode numbers
>       have already been assigned.

Would be great to have some numbers here, how this and the modifications 
to cpdup changes performance.

>     * Hints can now be passed to the block allocator.  The B-Tree code
>       now uses them to try to keep internal nodes more localized.  The
>       block allocator also now leaves a bit of empty space at the end
>       of the big-block for localized B-Tree expansion room.

I am trying to understand the hinting mechanism. So before this commit,
B-Tree nodes were always allocated physical linearly out of a big block,
while after this commit, you pass a hint, where the B-Tree node could or 
should physically be placed within a big-block, and if that space is not
yet allocated, the B-Tree is allocated at the hinted position. If the 
hinted position is already allocated, you simply fall back to linear 
allocation. That is how I understand it. I do not know how you calculate 
those hints.

Regards,
  Michael