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Regarding swap memory on HP-UX server.

Regarding swap memory on HP-UX server.

Hi,

I want to know how I can find the actual free physical memory in the system. When I use swapinfo –mat it shows I have 18.4GB of free physical memory. But in top it shows 5.5 GB of free physical memory. And also swap space is reserved fully i.e. 20.2GB. We have 32GB of RAM and 8 CPU. We are running SAP ECC6.0 and Oracle 10.2g Database. The swap space configured as priority one. I want to know if I change the priority of swap device file to 2 it will then use more physical memory and performance of system will improve. As currently all swap space is reserved fully. And also what is the formula to calculate the maximum swap space required for the system so that performance will improve.

 

Server1:[/]# swapinfo -mat

             Mb      Mb      Mb   PCT  START/      Mb

TYPE      AVAIL    USED    FREE  USED   LIMIT RESERVE  PRI  NAME

dev        8192      22    8170    0%       0       -    1  /dev/vg00/lvol2

dev        4000      22    3978    1%       0       -    1  /dev/vg00/lvswap1

dev        4096      21    4075    1%       0       -    1  /dev/vgmaxfs/lvswap2

dev        4096      21    4075    1%       0       -    1  /dev/vgmaxfs/lvswap3

reserve       -   20299  -20299

memory    25498    7058   18440   28%

total     45882   27443   18439   60%       -       0    -

 

Server1:[/]# top

System: Server1                                      Mon Oct 31 02:11:47 2011

Load averages: 1.01, 1.01, 0.92

376 processes: 348 sleeping, 26 running, 2 zombies

Cpu states:

CPU   LOAD   USER   NICE    SYS   IDLE  BLOCK  SWAIT   INTR   SSYS

 0    0.88  24.8%   0.0%  33.7%  41.6%   0.0%   0.0%   0.0%   0.0%

 1    0.97  30.7%   0.0%  41.6%  27.7%   0.0%   0.0%   0.0%   0.0%

 2    0.94  37.6%   0.0%  24.8%  37.6%   0.0%   0.0%   0.0%   0.0%

 3    1.03  21.8%   1.0%  39.6%  37.6%   0.0%   0.0%   0.0%   0.0%

 4    1.05  23.8%   0.0%  38.6%  37.6%   0.0%   0.0%   0.0%   0.0%

 5    1.06 100.0%   0.0%   0.0%   0.0%   0.0%   0.0%   0.0%   0.0%

 6    1.06  20.8%   0.0%  40.6%  38.6%   0.0%   0.0%   0.0%   0.0%

 7    1.06  21.8%   0.0%  35.6%  42.6%   0.0%   0.0%   0.0%   0.0%

---   ----  -----  -----  -----  -----  -----  -----  -----  -----

avg   1.01  34.7%   0.0%  31.7%  33.7%   0.0%   0.0%   0.0%   0.0%

 

Memory: 22143104K (6508996K) real, 25790364K (7640392K) virtual, 5589164K free  Page# 1/14

 

Thanks,

Narendra

3 REPLIES
Dennis Handly
Acclaimed Contributor

Re: Regarding swap memory on HP-UX server.

>what is the formula to calculate the maximum swap space required for the system so that performance will improve.

 

Increasing swap space won't improve performance.  Only increasing RAM or pseudoswap.

(And you probably want minimum instead of maximum. :-)

Re: Regarding swap memory on HP-UX server.

 

Hi Dennis

Thanks for the reply. Then please let me know both minimum and maximum swap space. And also what exactly the pseudoswap means?

 

Thanks,

Narendra

Dennis Handly
Acclaimed Contributor

Re: Regarding swap memory on HP-UX server.

>Then please let me know both minimum and maximum swap space. And also what exactly the pseudoswap means?

 

Pseudoswap is memory backed swap, RAM.  (See memory line.)

Minimum device swap is what you need to get your application to work.  If you want performance, you want to use as little device swap as possible.

 

>I want to know if I change the priority of swap device file to 2 it will then use more physical memory and performance of system will improve.

 

That won't change things.  As quoted by other experts on the forum, if you are worried about priority, you are just rearranging the deck chairs on the titanic.

 

>As currently all swap space is reserved fully.

 

Yes, your device swap is reserved but not used.  That's a good thing.