size limit for TMPFS

[Eric Anderson]

On 05/17/07 04:36, Howard Su wrote:
> In current implementation of tmpfs, the size limit of a tmpfs (which
> is passed when mounting) only count the file size. The memory used for
> directories is not limit. This due to the fact that there is not easy
> and fast way to track a uma_zone's memory usage.
> 
> there are several approach:
> 1. hack vm to support a hook when uma_zone allocate a new page. this
> approach comes from Rohit Jalan. This also need some new API in uma(9)
> uma_set_allocate_hook
> uma_set_deallocate_hook
> 
> 
> 2. Add a new API to uma(9) to report its memory usage. This will
> require traveling a link list inside uma_zone.
> uma_get_paged
> 
> 3. Guess a file number limit based on size if use doesn't specific
> explict, or get the number user sepcified. Use the number limit
> instead of size limit to limit the memory usage. This doesn't need any
> changes to uma. Also the implementation is clean.
> 
> I personally perfer way 3. Any suggestions?
> 


Track the memory usage on your own?  As you allocate, keep a counter and 
total up the usage outside of uma.  (3) sounds good, except it may not 
be accurate, and that could lead to confusion for someone.


Eric