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Memory Useage clearification.,,

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Kannandgl_1
Frequent Advisor

Memory Useage clearification.,,

Dear All,

I need to know the HPUX RAM memory (used & free). When I use the "top" command, I get three values:
My Physical Memory Size is 4 GB.
Memory: 1391544K (1004260K) real,1634660K (1151780K) virtual,40188K free Page# 1/
12.
2.when ever i am using swapinfo -a [
# swapinfo -a
Kb Kb Kb PCT START/ Kb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 9142272 64 9139136 0% 0 - 1 /dev/vg00/lvol2
reserve - 1374784 -1374784
memory 4174360 1041528 3132832 25%
]
command i am getting other values .Please any clarify and advice to me...

Thanks and regards,
Kanna




4 REPLIES
Suraj K Sankari
Honored Contributor

Re: Memory Useage clearification.,,

Hi,

For better understanding of these please read man pages of top and swapinfo.

Everytings are there into man pages

Suraj
Ganesan R
Honored Contributor

Re: Memory Useage clearification.,,

Hi Kannan,

In top output, Memory is not all of physcial, memory, it is:
Total physical memory in the system DEDICATED to text, data or stack segments for all processes on the system.
Total physical memory for runnable processes, as opposed to sleeping processes.
Total memory dedicated to text, data or stack segments for all processes on the system. Some of this is paged out to disk (that is, not all of this is in current physical memory.)
Total memory for runnable processes, as opposed to sleeping or stopped processes.
Physical memory the system considers to be unused and available to new processes. When this value is low, swapping is likely to occur.
For more about top, see top(1) man page.
Best wishes,

Ganesh.
Venkatesh BL
Honored Contributor
Solution

Re: Memory Useage clearification.,,

Ganesan R
Honored Contributor

Re: Memory Useage clearification.,,

swapinfo -tm example and explanation:


Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 288 83 205 29% 0 - 1 /dev/vg00/lvol2
reserve - 141 -141
memory 102 41 61 40%
total 390 265 125 68% - 0 -


dev line(s):

are the actual physical swap device(s)
show if swapping has actually occurred. In other words, the PCT USED column in the dev lines represents the value last attained during a previous period of swapping. This is analogous to the high-water mark that a flood leaves.
to check to see if swapping is currently occuring, use 'vmstat -v 5 5' to see if the 'po' (page outs) is sustained above 0.

reserve line(s)

indicate how much of the swap device(s) has(have) been set aside for memory should it need to be swapped.

memory line:

indicative of how much of pseudo-swap has been reserved
when present, indicates pseudo-swap is enabled (i.e. swapmem_on kernel paraemter is set to 1, which is the default.) The size of pseudoswap is calculated to be 75% of the size of RAM (a.k.a. memory.) In other words, it does not refer to acual physical memory use!!!! Pseudo-swap was designed specifically for large memory systems for which acutal swapping is never (or rarely) expected to occur, so thereâ  s less need to use actual physical disk space for swap. For more information, see swapmem_on(5) , which reads:

In previous versions of HP-UX, system configuration required sufficient physical swap space for the maximum possible
number of processes on the system. This is because HP-UX reserves swap space for a process when it is created, to
ensure that a running process never needs to be killed due to insufficient swap.
This was difficult, however, for systems needing gigabytes of swap space with gigabytes of physical memory, and those
with workloads where the entire load would always be in core. This tunable was created to allow system swap space to
be less than core memory. To accomplish this, a portion of physical memory is set aside as 'pseudo-swap' space.
While actual swap space is still available, processes still reserve all the swap they will need at fork or execute time from
the physical device or file system swap. Once this swap is completely used, new processes do not reserve swap, and
each page which would have been swapped to the physical device or file system is instead locked in memory and
counted as part of the pseudo-swap space.
total line:
the PCT USED value shown in the total line indicates how much swap space has been actually reseved for swap. When this percentage gets near 100%, processes will not start up (unable to fork process) and new shared memory segments can not be created.
Best wishes,

Ganesh.