topic Re: swapping vs. paging in Operating System - HP-UX

swapping vs. paging

Sanjeev gupta_2 — Sun, 17 Oct 2004 23:32:08 GMT

Hi
What is difference between "page out rate"/"swap out rate" and "page in rate"/"swap in rate"

Thx
Sanjeev Gupta

Re: swapping vs. paging

Muthukumar_5 — Sun, 17 Oct 2004 23:40:44 GMT

check this,

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=135098

HTH.

Re: swapping vs. paging

Muthukumar_5 — Sun, 17 Oct 2004 23:42:54 GMT

Sanjeev,

Just a note to you. You can get repeated questions from

search with ITRC forums(hp) with required keyword there.

Some more advanced options also given there. Try with your keywords and do get more informations.

HTH.

Re: swapping vs. paging

Sridhar Bhaskarla — Sun, 17 Oct 2004 23:52:36 GMT

Hi Sanjeev,

swapout and pageouts are usually interchanged. The pageout/swapout activity depends on three thresholds.

otsfree: There may be a lot of free memory pages and it is the upper bound below which the paging will not occur.

desfree: This is the number of free pages desired. This is actually the limit where the pageouts will begin. This is the lower bound to page outs.

minfree: The minimum amount of free pages. If the memory available falls below this line, it indicates thrashing and you can see the entire processes getting deactivated. And this is usually termed as swapping outs.

So, in the nut shell, we call 'pageouts' when the most inactive pages are pagedout and 'swapouts' when the entire processes are swapped out. The reversal of this activity is 'in's.

Memory mapped activity can also be seen as paging activity. The best way to figure out if it is really paging or not is to keep track of 'free memory'. You can see both pageouts and free memory using 'vmstat' command.

-Sri

Re: swapping vs. paging

Geoff Wild — Mon, 18 Oct 2004 07:33:30 GMT

Attached is a text whitepaper on HP-UX swap.

Rgds...Geoff

Re: swapping vs. paging

Ted Buis — Mon, 18 Oct 2004 20:24:24 GMT

HP-UX and most system really page. But since old habits are hard to break, people often say swap, even when they know that the system really is paging. HP-UX will only page-in what is needed, so page-ins are okay and expected. It is the page-out rate that should be zero or very close to it. Page-outs indicate that there is memory pressure and you either need to make more efficient use of what you have, buy more, or live with the likely poor performance.