@Michael Bronson lsof is used to list all the deleted files which are still on disk due to open file descriptors. Memory is not immediately freed because the running process still has an open file handle to the just-deleted file. After all, if a process is still trying to use a file, you probably don't really want the kernel to get rid of it the file. On Linux based machines filenames are just pointers (inodes) that point to the memory where the file resides which could be a hard drive or even a RAM-backed filesystem. Each file records the number of links to it: the links can be either the filename (plural, and also every time a file is opened, the process actually holds the "link" to the same space. Space/memory is physically freed only if there are no links left to the deleted file, So, while the processes have the files still opened, you shouldn't expect to get space/memory back. It's not freed, it's being actively used. This is also one of the reasons that applications should really close the files when they finish using them. HTH
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