On Thu, Feb 17, 2005 at 04:43:27PM -0800, Eugene Surovegin wrote:

On Thu, Feb 17, 2005 at 03:38:05PM -0800, Stephen Williams wrote:

quoted

My embedded system is structured such that the main user-mode
processes that are being run are downloaded and executed on demand.
I'm currently downloading the executable to an ext3 system on the
CompactFlash, but there is really no reason to use non-volatile
memory so I'm thinking to download to a tempfs directory and
execute from there.

But if I do that, I want to remove the program from the directory
after I start it, so that the file does not take up ram space. Will
that actually work? I'm using exec(2) to execute the program file
wherever it is downloaded. Will a subsequent unlink of the file
have a result, or will the file continue to take up space as
backing store for the executable?

I think unlink will remove the file from directory (so you won't be
able to see it with ls), but it will still continue to to take space -  
you're right it will be used as backing store, at least for read-only 
segments, which can be discarded if memory is tight. Even if you mlock 
all executable in memory, I think there will be still at least one 
reference to this file, which will prevent freeing tmpfs memory.

A little correction, according to tmpfs doc, it lives completely in 
page cache, so I think memory is not wasted for unmodified sections of 
the loaded file (e.g. a second copy, when file is executed and loaded 
into user-space, isn't being made).

But as usual, make some measurements first :)

--
Eugene.