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Excessive use of swap

 
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Carme Torca
Super Advisor

Excessive use of swap

Hi,

I have a system 11.23 with the following kernel parameters:

allocate_fs_swapmap 0 Default
dmp_swapdev_is_vol 0 Default
Default nswapdev 10
Default nswapfs 10
remote_nfs_swap 0 Default
swapmem_on 0 0
vol_swapdev_is_vol 0 Default
dbc_max_pct 20 20
dbc_min_pct 10 10

This is a DB server and when users begin to enter to the application, the swap consumption soars.

The server has the following use:

glb_mem_sys_and_cache: 30%
glb_ mem_user_util: 50% peaks

When there are these peaks glb_mem_user_util, the glb_swap_space_util up to 80% and also gbl_mem_util up to 80%.

Why does this happen?. I do not understand because the system consumes as much swap if memory has reached 80%.

Thank you very much,
Carmen.
Users are not too bad ;-)
4 REPLIES

Re: Excessive use of swap

>swapmem_on 0 0

The first thing you should do is turn this on and reboot.
What does "swapinfo -tam" show?
Carme Torca
Super Advisor

Re: Excessive use of swap

Now is:

>swapinfo -tam
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 4096 0 4089 0% 0 - 1 /dev/vg00/lvol2
dev 81920 0 81912 0% 0 - 1 /dev/vg00/swap1
dev 81920 0 81912 0% 0 - 2 /dev/vg01/swap2
reserve - 127017 -127017
total 167936 127017 40896 76% - 0 -


And this server has this memory:


vmunix: Physical: 125692692 Kbytes, lockable: 103163524 Kbytes, available: 105526848 Kbytes

What does swapmem_on do?. I don't know if someone change it to 0 for some reason.

Thanks,
Carmen.
Users are not too bad ;-)
Solution

Re: Excessive use of swap

>What does swapmem_on do? I don't know if someone change it to 0 for some reason.

It enables pseudoswap. If you don't have it on, you need swap for every page in memory.
Turning it on may give you 90+ Gb of swap.

There probably aren't any good reasons to have it off because on 11.31 it was removed and always on.
Carme Torca
Super Advisor

Re: Excessive use of swap

Thanks!!
Users are not too bad ;-)