On Sat, Jan 04, 2003 at 11:01:31PM +0100, Reinier Jonker wrote:

 > This does not seem logical to me. When the pages in swap are required 
 > again, there is a huge performance penalty when paging them back in. 
 > Wouldn't it be better to page swap pages back in during idle time if 
 > the amount of free memory permits that? I do see one disadvantage, it 
 > may be required to page them back out before the pages are used again, 
 > but it may be possible to reduce that disadvantage with a timeout

The reason for leaving them out in swap until they're needed again is
because the pages were "idle" in the first place (that's how they were
selected to go out to swap).  This means that they're likely to continue
to be "idle", and so leaving them there until they are actually needed
saves pointless I/O.

-- 
        -- Jason R. Thorpe <thorpej@wasabisystems.com>