Swapinfo VS Memdetail

[C_V]

Hey guys whats the difference of the device swap in swapinfo and memdetail how come they dont match?

In checking the swap usage of the server which should be follow, swapinfo or memdetail?

[Dennis Handly]

Do you have some actual output?

[Steven E. Protter · Accepted solution]

Shalom,

Two different utilities written, using two different concepts to report.

You might wish to provide an example of what the discrepancy really is.

SEP

[C_V]

Here is the sample:

$ /usr/sbin/swapinfo -tamd
Mb Mb Mb PCT Mb
TYPE AVAIL USED FREE USED START RESERVE PRI NAME
dev 2048 68 1980 3% 0 - 1 /dev/vg00/lvol2
total 2048 68 1980 3% - 0 -

$ /opt/HPO/SMSPIv2/bin/memdetail
Memory Stat total used avail %used
physical 1022.0 931.0 91.0 91%
active virtual 472.0 401.1 70.9 85%
active real 134.6 115.6 19.0 86%
memory swap 721.1 663.4 57.7 92%
device swap 2048.0 264.2 1783.8 13%

[Don Morris_1]

http://docs.hp.com/en/B3921-60631/swapinfo.1M.html

-d

Print information about device paging areas only. This modifies the output header appropriately.

When you tell swapinfo to only report on devices, you shouldn't be surprised when the memory swap line is missing.

"swapinfo -atm" should look right (memdetail and swapinfo certainly agree on what swapinfo reported).

[C_V]

- Here is another output from the server:

$ /opt/HPO/SMSPIv2/bin/memdetail
Memory Stat total used avail %used
physical 1022.0 935.4 86.6 92%
active virtual 471.7 407.9 63.8 86%
active real 137.4 121.7 15.7 89%
memory swap 721.1 663.4 57.7 92%
device swap 2048.0 263.9 1784.1 13%
$ /usr/sbin/swapinfo -tam
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 2048 66 1982 3% 0 - 1 /dev/vg00/lvol2
reserve - 198 -198
memory 721 663 58 92%
total 2769 927 1842 33% - 0 -

- When speaking of swap usage we are talking about device right?
- But how come the device swap usage is different from the memdetail and swapinfo.

[Ganesan R]

Hi Sigfred,

Where is device swap value is varied on memdetail and swapinfo output?

memdetail report:
------------------
device swap 2048.0 263.9 1784.1 13%

swapinfo report:
----------------
dev 2048 66 1982 3% 0 - 1 /dev/vg00/lvol2

both are showing 2GB as device swap. it is correct only...

[Dennis Handly]

>When speaking of swap usage we are talking about device right?

Not really. There is device and there is pseudo swap.

>But how come the device swap usage is different from the memdetail and swapinfo.

You are going to have to point to the difference. Ganesan and I don't see any, at least for the total. For pseudo swap, it is the same for all values.

For memdetail, it seems it doesn't separate the reserved line from the used device swap. Summing the two from swapinfo, matches.

[C_V]

Yes i think your right "For memdetail, it seems it doesn't separate the reserved line from the used device swap. Summing the two from swapinfo, matches."

Is the reserve line considered as a normal swap?

What is the purpose of this reserve swap anyway?

[Dennis Handly]

>Is the reserve line considered as a normal swap? What is the purpose of this reserve swap anyway?

The reserve line is just details of how device swap is used. It basically says that the space has been reserved but hasn't been touched or swapped back to disk yet.

[Don Morris_1]

And again, from the man page (which you really should read if you haven't):

reserve

Paging space on reserve. This is the amount of paging space that could be needed by processes that are currently running, but that has not yet been allocated from one of the above paging areas. See "Paging Allocation" below.

In other words -- the "reserve" line is how much of the swap from the device (or devices, or File System -- but here, just your single device) has been considered claimed for future swap needs if the time comes.

"Used" means that it really is in use -- there's actual data on the swap device, and there are processes which have claims to specific swap blocks.

Hence, memdetail sums up things to reflect how much device swap is used or reserved in order to give the best idea of how much is free to be claimed by new memory allocations.

[C_V]

- Thanks for the info guys! now i know!:)

[Dennis Handly]

If you are happy with the info you have gotten, please read the following about assigning points:
http://forums.itrc.hp.com/service/forums/helptips.do?#33