Can swap-in be improved?
Posted May 26, 2007 2:10 UTC (Sat) by giraffedata
In reply to: Can swap-in be improved?
Parent article: On-demand readahead
One thing that would improve this and various other things is actual swapping. What we call swapping in Linux is really just virtual memory paging. Swapping is a much older technology in which you remove an entire process from memory to let other processes run, then bring the entire process back when it's turn comes around again. It's also known as long term scheduling.
If Linux could notice that a process hasn't accessed any of its pages (hasn't run) in a long time, it could write all the resident pages out to contiguous swap space. The next time the process runs, it could read it all back.
Furthermore, if Linux is stealing a page that was accessed quite recently, it ought to steal them all and then wait a while before swapping them all back in again and swapping out somebody else.
By the way, it would be a mistake to believe that all that paging activity when you sit down to a long-idle session is Linux "swapping." A lot of it is reading in memory mapped program files. Speeding that up isn't as easy.
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