Hello,
with your help I'm beginning to understand !! It's very difficult to determine the true memory usage on hpux...
I'm confusing with the fact that every process on hpux will reserve a maximum space of memory on "swapdisk". So, it's normal on hpux to have a high percentage of swap space used even when server have a very little amount of applications running. But, it's a problem when disk is swapping continuously (you can see that with the "pi" and "po" metrics on vmstat output, right ?).
The other point is the weird behaviour of the system memory ( = main memory = physical memory = RAM ?). This memory is used as a part of the swap space if you activate an operating-system parameter : swapmem_on (by defautl is set to 1). At this time, the part of the system memory embedded in the swap space is called "pseudo-swap". In the HP documentation, I read that only three-quarters of the system memory could be used into swap space. Thus, I don't understand why I'm getting 16372M available on the "memory" line from my "swapinfo" output ?! From what HP says I would only have 12G available for the pseudo-swap ! My system has 16Go of physical memory or RAM.
As I wrote before, the main problem is the amount of "reserved" memory because it's a max value ! So, the values indicated by "swapinfo" are bigger than the actual memory used by the system. Look at this new output :
psd216:~# swapinfo -tm
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 24000 973 23027 4% 0 - 1 /dev/vg00/lvol2
reserve - 9876 -9876
memory 16372 4764 11608 29%
total 40372 15613 24759 39% - 0 -
In fact, only 5737M (4764+973) of swap space is actually used. That corresponds to 14% of the total swap space. In case of troubles or necessity, processes COULD require a maximum value of 9876M taken from the reserved memory. In this case, you will have a swap space full at 39%... Am I right on this point ?
I'm so sorry to make such troubles for nothing but I want to understand how memory management works on hpux !! Thanks again for all your patience and help ! Best regards,
Thomas
Here is some very useful documentation :
http://www.docs.hp.com/en/5965-4641/ch01s09.html#d0e4274
http://unix.ittoolbox.com/groups/technical-functional/hp-ux-l/swap-511113#
http://www.math.ntnu.no/~perhov/public/unix/memory.html
"lars ebeling" <user-1fecd3eafd52@xymon.invalid> a écrit sur 28/07/2006 07:16:42 :
Hi,
From hpux-meminfo you get the 95% = (Total-Free)/Total . When you start > HP-UX memory is used for "swapping" (up to 75%) and that is included in > (Total-Free). This is called pseudo-swap. This is controlled by the kernelparameter swapmem_on. By default it's on (=1).
Memory used by processes should be 16372 - 212 - 4770
29% of your memory is used for pseudo-swap.
30% of your swapdisk is used.
Everytime when a process is started space on you swapdisk is reserved,
so
that the process won't run out of swapspace when it's needed.
Total Available swap = Available memory + Available swapdevice
Total Used swap = Used memoryswap + Used deviceswap + Reserved
deviceswap
More confused now???
Regards
Lars Ebeling
----- Original Message ----- From: <user-bb3e9041f07f@xymon.invalid>
To: <user-ae9b8668bcde@xymon.invalid>
Sent: Thursday, July 27, 2006 2:46 PM
Subject: Re: [hobbit] Important ! HP-UX and the memory utilisation
Hello,
Thanks for your explanation ! I'm sorry to insist but it's a bit hard to
understand. I think the true problem is the "reserved" memory. It's a
maximum value and may not be used totally. For me, the real information is on the first line and given by the swapdisk. In my example, I got a
total of
24G for swapping (also called paging by HP) and only 23% is used.
Moreover, to determine the total physical memory used, a little script
called "hpux_memory" is launched. I got very different results between
this script and "swapinfo -Mm" :
bash-3.00$ ./hpux-meminfo
Total:16372
Free:212
So, on my hobbit display I got percentage of memory utilisation > 95%
whereas I got 29% with the other command !! Where is the truth ?!
bash-3.00$ /usr/sbin/swapinfo -Mm
Mb Mb Mb PCT
TYPE AVAIL USED FREE USED
memory 16372 4770 11602 29%
For the swap or paging memory, "swapinfo -dm" :
bash-3.00$ /usr/sbin/swapinfo -dm
Mb Mb Mb PCT Mb
TYPE AVAIL USED FREE USED START RESERVE PRI NAME
dev 24000 7264 16736 30% 0 - 1
/dev/vg00/lvol2
I got several servers with two or more swapdisks, so this command may be
launched :
psu106:/# /usr/sbin/swapinfo -dtm
Mb Mb Mb PCT Mb
TYPE AVAIL USED FREE USED START RESERVE PRI NAME
dev 8192 4906 3286 60% 0 - 1
/dev/vg00/lvol2
dev 8192 4908 3284 60% 0 - 1
/dev/vg00/lvol3
dev 6144 5735 409 93% 0 - 0
/dev/vg_swap/lv_swap01
total 22528 15549 6979 69% - 0 -
If you can explain me where I'm wrong I would greatly appreciate !
Thanks
again !
Sincerly,
Thomas
"lars ebeling" <user-1fecd3eafd52@xymon.invalid> a écrit sur 25/07/2006
18:05:31 :
From: <user-bb3e9041f07f@xymon.invalid>
To: <user-ae9b8668bcde@xymon.invalid>
Sent: Tuesday, July 25, 2006 2:34 PM
Subject: [hobbit] Important ! HP-UX and the memory utilisation
Hello,
I got some troubles with HPUX and memory values. With Hobbit, in my
memory
test, I got this :
Memory Used Total Percentage
Physical 16156M 16372M 98%
Swap 22117M 40372M 54%
Everything seems normal but for me, these numbers are high 'cause
this
server does nothing during the day. So, I connected to the server
and
ran
this command to see the available memory :
psd216:~# swapinfo -atm
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 24000 5474 18526 23% 0 - 1
/dev/vg00/lvol2
reserve - 11550 -11550
memory 16372 4754 11618 29%
total 40372 21778 18594 54% - 0 -
This output clearly shows an error in the Hobbit display. If you
look,
my
total swap memory is equal to 24000M not 40372M as shown in Hobbit
and
only 23% is used !! Apparently, the values for the swap memory test
are
taken from the last line and that's not correct !
Then I tried to execute the binary called "hpux-meminfo" in the
client
"bin" directory and I get this :
The 24000M is not swapmemory it is swapdisk, ie diskdevice configured to > be
used for swap.
The 16372 is swapmemory or pseudo-swap as HP name it. It is a part of
memory
that could be used used for swapping (or as I prefer paging). If you
have a
lot of memory it is more efficient to use memory for paging. When a
process
is started in HP-UX swapdisk is reserved for the process (reserve
above). If
that swap isn't used, it's is waste of diskresources.
It is a try to explain.
Regards
Lars Ebeling
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