Re: Linux Swap Partitions

From: Seth Arnold (sarnoldat_private)
Date: Sun Jul 28 2002 - 19:26:31 PDT

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    On Sun, Jul 28, 2002 at 03:58:46PM -0400, Samuel R.Baskinger wrote:
    
    [Samuel's description is very good, but I figured I'd clear up a few
    minor points.]
    
    > If memory is in particularly high demand and a whole 
    > process has been deemed idle, that whole process may be swapped out of 
    > the RAM and onto the virtual memory (again, the swap partition).
    
    Linux doesn't perform the old-style "swapping" of moving entire
    processes to swap space; it only performs paging. It is probably
    possible for all of a process's pages to be swapped out but the process
    would have to be very idle indeed.
    
    > 	So what of all this can you use? Well, most computer do not wipe or 
    > protect the swap partition by zeroing pages on it.  This means that *if* 
    > a file was swapped or paged out of memory and into virtual memory, then 
    > it *might* still be there.
    
    Files are swapped to a swap partition only for memory-based filesystems
    that can use swap as a backing store. I think Linux's tmpfs (shmfs) can
    do this, but files on other filesystems are going to be backed by
    whatever block device they came from originally.
    
    -- 
    "A mouse can be just as dangerous as a bullet or a bomb."
    -- US Representative Lamar Smith (R-Texas)
    
    
    



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