Memory Server Performance

[Carme Torca]

Hi,
I have a system with 4Gb's Memory.

The out of swapinfo:
#swapinfo -tam
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 4096 450 3646 11% 0 - 1 /dev/vg00/lvol2
reserve - 1754 -1754
memory 3142 2536 606 81%
total 7238 4740 2498 65% - 0 -


mtune -l -q dbc_max_pct
Parameter: dbc_max_pct
Value: 50
Default: 50
Minimum: -
Module: -
kmtune -l -q nbuf
Parameter: nbuf
Value: 0
Default: 0
Minimum: -
Module: -
kmtune -l -q bufpages
Parameter: bufpages
Value: (NBUF*2)
Default: (NBUF*2)
Minimum: -
Module: -

Could I know if the system is ok with memory or need more?
Thanks!
Carmen.

[Pete Randall · Accepted solution]

Carmen,

You are doing some swapping which is always an indication that you could use more memory - for best performance you would rather never swap, but a little bit once in a while is OK.

You also show dbc_max_pct of 50. This should be reduced to 10, giving you about 400MB of cache. You may be able to further tune it but 400MB is usually a pretty good number. This will free up some memory.

I would suggest you adjust dbc_max_pct first and then take another look at usage and performance.


Pete

[Carme Torca]

Hi,

and how you see that??
Maybe its better to doen't have memory in swap?? How I calculated if I need more memory or no in a system?, for example I have 4Gb of memory and the swapinfo tells me that information.... is there any calcul to know that the system is ok or no?

Thanks very much!!!

#swapinfo -tam
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 4096 450 3646 11% 0 - 1 /dev/vg00/lvol2
reserve - 1754 -1754
memory 3142 2536 606 81%
total 7238 4740 2498 65% - 0 -

[Tim Sanko]

Carmen,

The question is not if you swap, but when.

If it is in core business hours, that is not good as swapping is slow. It becomes dollars and sense.

Is the swapping affecting performance?

You Bet it is. Is it worth adding RAM. That is a $$$ call.

I would reduce the minimum to 10% and ignore the max. It won't get there if you are swapping. Caching is good if you have spare ram. My Max is 50% but I have 32GB...
Different box different problems.

I have 8GB hypers and have 50 mounted and bcv'd and an extra several terrabytes extra for non DB files on the V2600. We found it was better to load the box with ram, and let the user community pay for it.