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: > > 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.
