RAM upgrade & kernel parameters

[Ramesh.K.R.]

Hi,

If i upgrade the RAM on a K570 server, say from 1.5 GB to 2.5 GB, do i have to tune the kernel(parameters) ??. If so, what are they & by what extent they should be tuned ??

Thanks & Regards,
Ramesh.K.R.

[T G Manikandan]

There is no need to increase the kernel parameters unless there is a need for that.

why are you upgrading the RAM on that machine?

how is the performance on that machine

[Steven E. Protter]

No required kernel parameter changes.

But this does allow you to raise shmmax which makes all those shared memory happy database applications run better.

shmmax can be up to 25% of total memory, which is defined as swap plus ram.

You also need to make sure swap is adequate. To hold a dump it must be at least 50% of ram. For a properly tuned system, probably 1.0 to 1.5 times RAM.

You probably have nothing to worry about. My guess is you are upgrading RAM to deal with a slow system, which might have too much swap.

I'm adding a performance data collection script that might be useful in tuning.



SEP

[Ramesh.K.R.]

HI,

Thanks for your really quick response. I was also of the same openion. But, i wanted to cross check. We are increasing the RAM to get better performance from the application we have loaded on the m/c.

Regards,
Ramesh.K.R.

[Michael Tully]

You may want to check the dbc_min_pct and dbc_max_pct (buffer cache). You may need to lower the values (which are in percentages). The ideal setting is between 300 and 500MB for dbc_max_pct. I usually use around 150-200MB as a minimum.

[T G Manikandan]

Most of the kernel parameters does not have to be tuned unless the application/OS throws errors.(just stay with the default).

There are some parameters which are to be tuned for the application installation/performance.

If your application is running slow
I would suggest to check the parameters like maxusers,nproc,semaphore related kernel paramters which takes up too much initial memory on the system(locked memory).


Just check whether those parameters are really required so large values.
One of the parameters like buffer cache as pointed out above can be reduced.

This is a big subject to work thru'.Any parameters tuning should be done one by one and check the results for performance.

What application you are running?
Is your OS running 32 bit?

Is the system crunching for memory ?
If this is for that then upgrade the RAM.Put some extra swap and monitor the applicaiton.
How about the processor time usage.YOu can use
sar -u to find that out.
check the I/o of the application.

Revert