lotsfree - desfree - minfree

[Fabio Acquarone]

Hi to all,

i have a question regarding kernel parameters lotsfree - desfree and minfree. Is it true that these parameters are tunable ??
In which way ?
Using SAM (11.00 , 11i) i am not able to see these parameters even if using kmtune or sysdef they are present. (also other parameters ...)

Have you some information that can help me to understand this behaviour ??
I have an issue with the swap partition, seems that the paging is not properly configured..

Fabio

[Balaji N]

hi
may be these links help.

http://docs.hp.com/hpux/onlinedocs/os/11.0/tuningwp.html
http://docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/5965-4641/5965-4641_top.html&con=/hpux/onlinedocs/5965-4641/00/00/11-con.html&toc=/hpux/onlinedocs/5965-4641/00/00/11-toc.html&searchterms=lotsfree%7cdesfree&queryid=20030414-013907

hth
-balaji
members.irtt.org/~balaji

[Fabio Acquarone]

Thank you for the links...but as i know documents states that parameteers are tunable.....but i don't know how to tune it.

In which way i can reach these variables ???
I have to go directly inside the kernel structure and change it in the tune.h header file????

Fabio

[Michael Steele_2]

http://docs.hp.com/cgi-bin/otsearch/getfile?id=/hpux/onlinedocs/os/11.0/tuningwp.html&searchterms=desfree%7clotsfree&queryid=20030414-060915

lotsfree, desfree and minfree
There are three kernel parameters that have recently become tuneable by mortals. They are the "paging" parameters lotsfree, desfree and minfree. These parameters define thresholds that the kernel uses to determine swapper/vhand (the page daemon) behavior. Here is the short version, in english (sort of :-)), of how these parameters are used...

lotsfree -- vhand begins to "age" pages. There is another parameter that is dynamically modified, gpgslim, which is where vhand begins to "steal" pages. gpgslim starts at one quarter the distance between desfree and lotsfree, and "moves" between them, based on memory pressure.

desfree -- more serious, more furious :-) paging begins here. Much of vhand's behavior is modified at this point... how often it wakes up, how many pages to look at, what is the distance between the age and steal hands, how many pages to steal, etc.

minfree -- at this point, the system is deactivating processes. In the "old" days this would have been where swapping took place. We no longer swap processes.

I have noticed, on several occasions, that these parameters have been set way too high. It was very apparent on several V class machines. The suggested values are:

on a system with up to 2GB of memory:

lotsfree no larger that 8192 (32MB)
desfree no larger than 1024 (4MB)
minfree no larger than 256 (1MB)
on a system with 2GB to 8GB of memory:

lotsfree no larger than 16384 (64MB)
desfree no larger than 3072 (12MB)
minfree no larger than 1280 (5MB)
on a system with a whole group of memory:

lotsfree 131072
desfree 32768
minfree 8192


If you are having an issue with paging and swap then please attach swapinfo and vmstat.

vmstat 5 5
swapinfo -tam

[Michael Steele_2 · Accepted solution]

To read system file in /stand/build/system :

kmtune -s lotsfree -S /stand/build/system

To read system file in /stand/system:

kmtune -q lotsfree

To change in /stand/build/system:

kmtune -s lotsfree=###### -S /stand/build/system

mk_kernnel -s /stand/build/system

kmupdate /stand/build/system_test
cd /
shutdown -r now