Swapout and Pageout

[nibble]

Guys, just a quick question. In the memory parameters what's the difference between swapout and pageout as well as swapin and pagein?

[Jeeshan]

hi

page-out => The system's free memory is less than a threhsold "lotsfree" and vhand daemon used "LFU" algorithm to move some unused / least used pages to the swap area.

page-in => One process which is running requested for a page that is not in the current memory (page-fault), vhand daemon is bringing it's pages to memory.

swap-out => System is thrashing and swapper daemon has de-activated a process and it's memory pages are moved into the swap area.

swap-in => A deactivated process is back to work and it's pages are being brought into the memory.

[Matti_Kurkela]

Most modern systems use paging instead of swapping if at all possible, because paging is more fine-grained. It's just that the names "swap partition/swap file" and "swapping" are stuck for historical reasons, and they're being used sometimes even when what actually happens is paging.

If a modern server needs to swap/page out an active process, it's an indication that the server has a serious shortage of memory.

MK