Re: Max. number of subdirectories dump

[Manuel Wiesinger <manuel%bsdstammtisch.at@localhost>]

On 08/19/13 09:31, David Laight wrote:
> For defrag I'd have though you'd work from the inode table and treat
> directories no different from files.
That's what I'm doing.

I have an additional optimisation step, which tries to move files in the 
same directory, so that they are stored contiguously. This can improve 
performance, when a whole directory is read. That's why I iterate the 
directories. See my mailinglist posting and status update for more details.

> You would need to scan directories if you decide to renumber inodes,
> but since they are indexed that may not gain much.
I thought about that, but I agree that the gain is too little.

> It might be worth rewriting directories in order to remove gaps and
> possibly put subdirectories first (but you really want the most frequently
> used entries first).
That is exactly my idea. Good point with the most recently used entries 
first. But it's hard to find out which are the most recently used files. 
I think of storing directory entries first, then the files. But I'm not 
sure if this is the best approach.

Anyhow, this step is no official goal, so I don't focus on that now. 
When time allows I will implement it. Maybe even after GSoC.

> FYI A well known british internet payment scheme fell over when the 32768th
> vendor account was added onto the live system!
> (Solaris crash badly)
Ouch, this may be the reason, why it is mentioned in the Oracle docs.

Manuel