On Wed, 8 Mar 2000, Kiran Jonnalagadda wrote:
> What they have is not just hard links. It's a non-realtime scanner that
> computes signatures for all files on disk and then makes hardlinks for
> duplicate files. The hard link isn't permanent -- any of these files
> gets a new copy when modified. The idea is to cut down on space lost to
> frequently duplicated but rarely modified files. The /etc/skel directory
> for example.
>
> This is a feature that Linux file-systems could benefit from. It's not
> something to be laughed at.
The linux file system could do with it - yes. This feature however is
something that was an innovation in the linux process handling code.
Unlike normal multi-processing / multi-threading os's, linux does not
create an entire copy of a process' data area and files and stuff when it
forks. Instead, it waits for one of the two (identical) processes to
write to an area of memory (that is currently common to both). At this
point, it creates a copy of only that piece of data.
The idea is that most parts of shared data may (implicitly) be read only,
so there really is no reason why both processes shouldn't use the same
copy. Saves memory as well as time lost while making copies.
Just thought that this would be of interest to you'll
Philip
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