Operating System - HP-UX
1748128 Members
3580 Online
108758 Solutions
New Discussion юеВ

Re: Kernel parameters for Smallworld

 
RogerVI
Regular Advisor

Kernel parameters for Smallworld

Hi,
I have a Smallworld CST running in HP-UX 11.11 and I want to configure it for optimum performance.
I have two parameters that I want tune: dbc_min_pct and dbc_max_pct.
The server have 12 GB of physical memory and dbc_min_pct = dbc_max_pct = 10

The performance of Smallworld is better with more memory for the buffer cache ?
Please, provide me any clue or information according your experience.
Thanks in advance
Peter
Roger
15 REPLIES 15
Andrew Rutter
Honored Contributor

Re: Kernel parameters for Smallworld

hi,

it depends upon what the system needs really, number of open files...

see this link if you havent already, it may help you work out what may be best

http://docs.hp.com/en/939/KCParms/KCparam.DBCminPct.html

Andy
Manix
Honored Contributor

Re: Kernel parameters for Smallworld


Use "SAR" to monitor the buffer cache utilization as then tune it accordingly
using kctune -s =value

$ sar -b 1 10

http://h30499.www3.hp.com/t5/System-Administration/Setting-of-dbc-max-pct-and-dbc-min-pct/m-p/4542185#M369519


Thanks

Manix

HP-UX been always lovable - Mani Kalra
Jose Mosquera
Honored Contributor

Re: Kernel parameters for Smallworld

Dynamic Buffer Cache is the area of memory used by programs when writing to disk. Programs write to buffer cache instead of disk to speed things up.
The cache is then written in large chunks to disk during quieter periods. The time for this in very small figures in milliseconds.

The amount used being dynamically allocated dependant upon system requirements.

At times during system usage a high amount of dynamic buffering can be called for by the OS (i.e backup operations).

The state of buffer caching can be monitored by examining the field %rcache displayed from the sar -b command.

%rcache : Give you the read cache percentage.

This is the most important measurement tool for a resize of buffer cache max setting - 100% means that the systen is finding what it wants 100% of the time in dynamic buffer and is not searching slower systems for data (disk drives). A 99% is very good value.

If the dbc_max_pct is changes to a lower value then the %rcache is the value to monitor to ensure that the reduced size is not forcing the systen to "Look elsewhere".

This in itself will not give a performance increase but will release memory to be used by other system rescources, login, logout, cleanup after vdxusers, etc.

Rgds
Rita C Workman
Honored Contributor

Re: Kernel parameters for Smallworld

If you want kernel tuning assistance, than it would be helpful if you would supply:

1. List of your current parm settings
2. Output of swapinfo -tam
3. Output of sar -v 1 10

That will give folks here at least a little bit more info...

Now for a couple of my favorites to tune:

dbc_max% I'd set it at 10-12
dbc_min% I'd set it at 5

I would run sar -v 1 10 and probably change my ninode to something closer to what the output shows you really need.
With 12Gb of memory I would change the vx_ninode from zero to something more like 40,000 to 60,000.

The outputs from above will help us see what else might be tuned or give folks a clue as to what next to ask...

Kindest regards,
Rita
RogerVI
Regular Advisor

Re: Kernel parameters for Smallworld

I've attached:

1. List of your current parm settings
2. Output of swapinfo -tam
3. Output of sar -v 1 10
Roger
Rita C Workman
Honored Contributor

Re: Kernel parameters for Smallworld

hmmm...I can't download this.

Can you post some of it..

Rita
RogerVI
Regular Advisor

Re: Kernel parameters for Smallworld

I've attach the file kmtune.txt
Roger
Jose Mosquera
Honored Contributor

Re: Kernel parameters for Smallworld

What about of sar -b output?
RogerVI
Regular Advisor

Re: Kernel parameters for Smallworld

I've attached sar -b 1 10

Roger