topic Re: High page out rate in 11.31 in Operating System - HP-UX

High page out rate in 11.31

ESCDEMO — Thu, 23 Dec 2010 05:44:28 GMT

Hi,

I have installed the 11.31 on BL890C server,and filecache_max is only 3% of total 64GB memory. But I found the page out rate is over 10%, although the memory utilization is around 50%. Could anyone explain why the page out rate is high? Thanks!

Re: High page out rate in 11.31

Dennis Handly — Thu, 23 Dec 2010 07:26:06 GMT

The high PO rate seems to only occur during certain times. Do you know what's going on then?
These could be large mmapped files being flushed. Or large shared memory segments.

Re: High page out rate in 11.31

ESCDEMO — Tue, 04 Jan 2011 08:11:28 GMT

Hi,

Thanks for yur reply! But I had never seen the page out rate on 11.23 using OVPM while free memory is large.

Re: High page out rate in 11.31

Don Morris_1 — Tue, 04 Jan 2011 14:31:30 GMT

Buffer cache flushes on v2 are not counted as pageouts. On v3, however - since the file and buffer caches are unified, the same mechanism flushes that cache -- which means that file cache management will generate pageouts. Assuming that your 3% file cache results in the contents of the cache being pushed out due to the referenced file space being larger, that could easily account for the difference in behavior.

Re: High page out rate in 11.31

Ismail Azad — Tue, 04 Jan 2011 20:28:02 GMT

Hi,

What don is talking about is the concept of something called as UFC or the unified file cache which takes away the concept of storing file access data and memory mapped file data being implemented as seperate caches which are controlled by different system calls to provide better coherency .Unified file cache is a feature of 11.31. Do assign points for folks who have helped you if you find the answer useful.

Regards
Ismail Azad

Re: High page out rate in 11.31

ESCDEMO — Wed, 05 Jan 2011 09:03:45 GMT

Thanks for your explanation!