> Would someone please shed light on the following for me. What is the > dif from swaping to paging other than swaping is using the swap > space? I can't seem to find much info on paging? I believe if I'm > swapping heavily that's bad, but where does the pageing go and is it > bad for perf? THANX!!! > > % Swap space used 0%
This tells you that you are not using any of your swap space, so your virtual machine is probably large enough that no Unix paging needs to occur. > Swap-in rate 0/s > Swap-out rate 0/s In traditional Unix systems, virtual memory is page oriented, but if the virtual memory system becomes sufficiently stressed, the kernel will attempt to move entire processes to swap to free up the maximum number of pages with one operation (it's a crude sort of block paging approach without actually doing I/O optimization). This number indicates the number of times this has occurred. In versions of Unix without virtual memory (2.9 BSD and that ilk), this was the only way to overcommit memory. Swapping on PDP11s was very common, especially on the smaller 11/05 and 11/23 systems. VM/HPO used to have this ability (separate swapping and paging, and the ability to prioritize one over the other to different disk areas), but that ability was lost with the transition to VM/XA (restored by a 3rd party set of CP mods). This transaction really impacted the sales of solid-state disk units -- swapping to SSD first was a really nice performance boost on memory-constrained systems when we still had a 16M cap. Even on the 1st generation XA systems (308x), HPO was a real win. > Page-in rate 0.066/s > Page-out rate 50.133/s This is normal dynamic paging activity, eg pages/sec. As someone else said, if this is database activity, it's probably sending things out and then rebuilding the page internally instead of trying to pull it back in from paging space.
