Re: [lc-devel] Compressed TMPFS

[Nitin G. <nit...@gm...>]

Hi,

On 4/28/07, Jun OKAJIMA <ok...@di...> wrote:
>
> 1. Can I understand the project as a linux version of "RAM Doubler" ?
>    ( RAM Doubler is an interesting util for Macintosh in old days. )
>    "Compressed Cache" compresses main memory. Not only cache, but whole mem. Right?
>

"Compressed Cache" compresses parts of memory which would otherwise be
swapped or put back on disks when you are running low on memory. So,
it does not compress _whole_ memory but only certain amount
(configurable) of such relatively unused memory (essentially reducing
costly disk I/O).

> 2. What I need is, so called "compressed tmpfs", in other words,
>    I need a DBLSPACE of MSDOS for RAM disk.
>    This project can work for my purpose?
>

If I understand, you require in-memory filesystem that compressed
_all_ its contents. This is not what ccaching does.

> 3. Do you have any figure which shows performance improvement of compressing?
>    As you must know, there seems to be a trade-off about CPU usage and memory
>    efficiency. Compressed Cache really improves the performance? If so,
>    how much in what case?
>

No performance figures yet. Still I am working on stabilizing it!
An important feature of automatic ccache resizing based on workload is
still missing. So, any performance figures will be highly tied to kind
of benchmark load you use.


Cheers,
Nitin