cancel
Showing results for 
Search instead for 
Did you mean: 

Question about swap

 
SOLVED
Go to solution
Subentu
Frequent Advisor

Question about swap

Guys,

I have a Rx7620 system running HP-UX 11.23

This is the memory utilization of the system during the peak workload (taken using kmeminfo):

Physical memory = 4183868 16.0g 100%
Free memory = 30012 117.2m 1%
User processes = 3399628 13.0g 81% details with -user
System = 739281 2.8g 18%
Kernel = 530089 2.0g 13% kernel text and data
Dynamic Arenas = 249295 973.8m 6% details with -arena
vx_buffer_cache = 76512 298.9m 2%
vx_global_pool = 26964 105.3m 1%
VFD_BT_NODE = 23976 93.7m 1%
vm_pfn2v_arena = 16636 65.0m 0%
SWAP_MISC_ARENA = 16526 64.6m 0%
Other arenas = 88681 346.4m 2% details with -arena
Super page pool = 9504 37.1m 0% details with -kas
Static Tables = 209118 816.9m 5% details with -static
pfdat = 98063 383.1m 2%
nbuf = 54400 212.5m 1% bufcache headers
vhpt = 32768 128.0m 1%
bufhash = 8192 32.0m 0% bufcache hash headers
text = 6402 25.0m 0% vmunix text section
Other tables = 9292 36.3m 0% details with -static
Buffer cache = 209192 817.2m 5% details with -bufcache
UFC file mrg = 0 0.0b 0%
UFC meta mrg = 0 0.0b 0%



And this is the # swapinfo -tam output at the same time:

Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 4096 2049 2047 50% 0 - 1 /dev/vg00/lvol2
dev 12000 2051 9949 17% 0 - 1 /dev/vg00/lvol10
dev 16500 2049 14451 12% 0 - 1 /dev/vgswap/lvol1
reserve - 13754 -13754
total 32596 19903 12693 61% - 0 -

(outputs are attached also, if they are not clear)

My question is it normal that the free memory is so low (1%) when there is only 50% of the swap is used ?

Thanks in advance.
5 REPLIES
Solution

Re: Question about swap

You should immediately enable swapmem_on(5), why was it turned off?

>is it normal that the free memory is so low (1%) when there is only 50% of the swap is used?

There is no direct connection between swap used and free memory, if you are using more swap than memory.
The whole purpose of HP-UX is to use all of memory as possible and not use device swap.
13 Gb is for users, out of 16 Gb.

Any particular problem you are trying to solve?
Avinash20
Honored Contributor

Re: Question about swap

If you are facing any performance issue, then I would advise to increase the physical memory or decrease the load on the users on this server.
User processes = 3399628 13.0g 81% details with -user

# ./kmeminfo -user
<< to get list of user processes consuming physical memory >>
"Light travels faster than sound. That's why some people appear bright until you hear them speak."
Emil Velez
Honored Contributor

Re: Question about swap

The reason you are using swap is because you are using all of your physical memory.

I would consider setting dbc_max at 2-3 %
That will free up physical memory without impacting the system much


or you need more physical memory.

Venkatesh BL
Honored Contributor

Re: Question about swap

You could use kmeminfo -user to see details of the processes using that much memory. See if all is in order.
Bill Hassell
Honored Contributor

Re: Question about swap

> is it normal that the free memory is so low (1%) when there is only 50% of the swap is used?

Of course this is normal. Swap is not used until you run out of memory. Without all the details, you can be using 1% of swap when 100% of memory is used. You are using a *LOT* of swap space and this implies that you are short of memory. Verify this by running vmstat 1 5 when the system is running slowly. The column po (page out) indicates how bad you need memory. Single numbers are fine, 2 digits up to 20-30 are OK but over 50 means you are wasting a lot of time waiting for pages to be swapped in/out.

Swap and performance are opposites -- swap allows you to run with limited memory, as long as you can wait for slow processing.


Bill Hassell, sysadmin