Question regarding memory disks

[Julian Elischer]

Ulrich Spörlein wrote:
> On Wed, 06.01.2010 at 16:27:09 -0800, Julian Elischer wrote:
>> Pieter de Goeje wrote:
>>> Because when you "erase" something, all it does is unlink (delete the 
>>> reference to) the data. So there is currently no way the memory disk can free 
>>> the memory associated with the data. That is also why you should normally use 
>>> swap backed memory disks instead, or use tmpfs. These can return memory to 
>>> the system.
>>>
>>> The ability of the filesystem to mark certain blocks as "erased" is important 
>>> not only for memory disks but also for solid state drives. It is a feature 
>>> UFS2 is currently lacking unfortunately.
>> but is being worked on
> 
> Will this automagically work for md(4) backed UFS2 file-systems? Is this
> also being worked on?

that will depend on md

there are two patches out there that use the VFS DELETE command under 
UFS to free unused space. how that operation is handled depends on the
lower level.

Disclaimer: I have seen the patches but are not using them. I believe 
Mav and Jeff have both looked at this and Kirk showed a path that was
similar to Jeff's.



> 
> Regards,
> Uli