Paul,
When tuning "maxperm", one important thing should be noted:
"maxperm" is not the limit on cached file pages! Under heavy JFS file
I/O, the file cache can grow up to "maxperm" by paging out process
data areas (I think AIX documentation refers to them as
"computational" pages) - if there is free memory beyond maxperm, the
file cache will continue to grow and consume all available free
memory. In other words, maxperm defines the limit where the file
cache will *compete* with processes for memory.
So if you have a system with a known "small" application load and no
real need for VM paging, I don't see a reason why not to set maxperm
very low, to let the file cache only consume real "free" memory.
As an example, here's one of our boxes:
number of valid memory pages = 2097141 maxperm=8.0% of real memory
maximum pinable=80.0% of real memory minperm=3.0% of real memory
number of file memory pages = 847688 numperm=40.4% of real memory
Of course, I'm pretty sure if you use raw logical volumes, all of this
goes out the window. Our TSM server is a Sun (with raw logical
volumes), so I can't tell exactly how AIX will behave.
Cheers,
Paul Ripke
UNIX/OpenVMS Sysadmin
CSC, Port Kembla 2502, NSW, Australia
Phone +61 2 4275 4101
Fax +61 2 4275 7801
Mobile +61 419 432 517
101 reasons why you can't find your Sysadmin:
68. It's 9 AM. He/she is not working that late.
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