topic Re: top and huge virtual memory problem in Operating System - HP-UX

top and huge virtual memory problem

Dejan Donovski — Wed, 31 Aug 2005 08:01:32 GMT

Hi

I have a problem regarding the amount of the virtual memory on rx2600 server with 4GB RAM.
top shows:

Memory: 895972K (162544K) real, 30980256K (4965800K) virtual, 91600K free

and swapinfo shows:
Kb Kb Kb
TYPE AVAIL USED FREE USED
dev 4194304 122896 4071408 3%
reserve - 2462276 -2462276
memory 3103596 2991128 112468 96%

i can see that pseudo-swap is turned on (3GB) an that it is used 96%. However i am confused about the way top calculates the memory.
How can the virtual memory be 30GB when there is 4GB swap space and 4 GB RAM? Where would the memory above the 8GB limit be allocated?
Is the 900MB real memory in the top output,calculated as the ammount of physical memory minus the 3GB (75%) pseudo-swap?

Re: top and huge virtual memory problem

Bill Hassell — Wed, 31 Aug 2005 09:01:30 GMT

top's memory report is almost useless as it does not calculate the numbers in a meaningful way. Most likely you are missing a patch for top, but use swapinfo for this information, but always use swapinfo -tm. The last line is more meaningful. You have 4Gb of swap with 4Gb of RAM so you won't run out of virtual memory until your virtual memory usage hits about 7Gb. Glance is the only program that will give you an accurate picture of memory usage. Note: the majority of "out of memory" errors have nothing to do with RAM or virtual memory.

Re: top and huge virtual memory problem

Cem Tugrul — Wed, 31 Aug 2005 09:08:17 GMT

As an addition to Bill,

Re: top and huge virtual memory problem

Steve Steel — Wed, 31 Aug 2005 10:01:59 GMT

Hi

Look at

ftp://eh:spear9@hprc.external.hp.com/memory.htm

I. Memory Usage as seen in "dmesg", "swapinfo", "top", "sam", and "glance"

Steve Steel

Re: top and huge virtual memory problem

Dejan Donovski — Thu, 01 Sep 2005 05:12:56 GMT

Thanks for your advices,
swapinfo -tm produces:

Mb Mb Mb PCT
TYPE AVAIL USED FREE USED
dev 4096 132 3964 3%
reserve - 2303 -2303
memory 3031 3031 0 100%
total 7127 5466 1661 77%

I can see that there is not enough memory.
The server is running oracle with many processes, however i can not find out exactly
how much memory is alocated by each process
becouse when i do:
UNIX95=1 ps -efo vsz,sz,pid,args
VSZ SZ PID COMMAND
382976 14961 10417 oracleorahp (LOCAL=NO)
382976 15057 12381 oracleorahp (LOCAL=NO)
382976 15082 12580 oracleorahp (LOCAL=NO)
382976 15017 12318 oracleorahp (LOCAL=NO)
382976 14982 12203 oracleorahp (LOCAL=NO)
382976 15040 10759 oracleorahp (LOCAL=NO)
(this is only part of the output)

if i calculate the ammount of virtual memory as number of pages*4096 it turns out that
each of those processes has 1.5GB virtual
memory which is impossible. I guess that for accurate numbers glance must be used.

Re: top and huge virtual memory problem

Steve Steel — Thu, 01 Sep 2005 05:30:46 GMT

Hi

get procsize from the website I gave you

c) Can look at shared memory usage by process with an unsupported utility called procsize, which breaks down memory by various types, specifically: UAREA, TEXT, DATA, STACK, Shared Memory, Memory Mapped files.

For example:
Look at breakdown of memory usage, per process:

# ./procsize -fnc | more
pid Comm UAREA TEXT DATA STACK SHMEM IO MMAP Total
2916 getty v 4 5 6 4 0 0 349 369
2287 prm3d v 68 6 671 513 0 0 37212 38471
.
.
.

TRICK: Here's the command to use to sort the processes by total memory usage, most to least.

# ./procsize -fcn |sort -rnk 11 | more

TRICK: Here's the command to use to sort the processes by shared memory usage, most to least.

# ./procsize -fcn |sort -rnk 8 | more

Then you have good figures

I think the oracle uses the SGA so they all show the same 1.5 gig

Steve Steel