Low Memory utilization but high paging.

[roel_hawk]

Hi,

Our server have low memory utilization but high paging (in and out).

What do you think caused this?

Roel

[roel_hawk]

To add some more detail:

The memory utilization is constant at 4% but the page in and out values are more than 20.

rgds,

Roel

[Jaime Bolanos Rojas.]

Roel,

Please send us the output of those two commands,

swapinfo -tam

vmstat 5 20

Regards,

Jaime.

[roel_hawk]

Hi Jaime,

Here is the output.

# swapinfo -tam
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev 4096 0 4096 0% 0 - 1 /dev/vg00/lvol2
dev 20000 0 20000 0% 0 - 1 /dev/VGSAP/LVSWAP
dev 20000 6874 13126 34% 0 - 0 /dev/VGSAP/LVSWAP2
reserve - 26912 -26912
memory 12730 504 12226 4%
total 56826 34290 22536 60% - 0 -
# vmstat 5 20
procs memory page faults cpu
r b w avm free re at pi po fr de sr in sy cs us sy id
1 0 0 3806598 18198 27 13 23 24 5 0 12219 2749 12479 1151 6 1 94
1 0 0 1901456 17588 36 30 3 0 0 0 0 2255 17059 2277 3 1 95
1 0 0 1901456 18151 11 9 2 0 0 0 0 2211 7021 934 1 0 99
2 0 0 1979880 18134 3 2 3 0 0 0 0 2218 4650 521 2 0 98
2 0 0 1979880 18134 13 12 0 0 0 0 0 2238 3663 325 1 0 98
1 0 0 920343 17819 18 3 24 0 0 0 0 2236 2694 310 1 0 99
1 0 0 920343 17819 18 12 8 0 0 0 0 2221 1548 226 1 0 99
1 0 0 946779 17819 9 3 4 0 0 0 0 2221 1118 195 0 0 100
1 0 0 946779 17766 16 12 6 0 0 0 0 2216 1971 243 1 0 98
1 0 0 1060567 17789 5 3 1 0 0 0 0 2223 1651 233 1 0 99
1 0 0 1060567 17678 16 12 10 0 0 0 0 2226 1307 212 0 0 99
1 0 0 1051999 17646 5 3 7 0 0 0 0 2221 1240 203 1 0 99
1 0 0 1051999 17628 17 13 4 0 0 0 0 2223 1351 201 1 0 99
1 0 0 4079376 17576 12 8 0 0 0 0 0 2250 11982 1241 5 1 93
1 0 0 4079376 17576 20 16 0 0 0 0 0 2226 4651 528 1 0 99
1 0 0 4060792 17571 18 14 0 0 0 0 0 2234 2229 429 0 0 99
1 0 0 4060792 17568 22 18 0 0 0 0 0 2221 1350 259 0 0 100
1 0 0 673852 17274 8 4 30 0 0 0 0 2220 868 208 1 0 99
1 0 0 673852 17266 17 15 12 0 0 0 0 2211 1493 233 1 0 99
1 0 0 710292 17262 5 4 4 0 0 0 0 2209 775 188 0 0 100

thanks,

Roel

[Jaime Bolanos Rojas.]

Roel,

Thanks for the output, one thing, usually when it comes to paging, you want to pay special attention the po column out of the vmstat command, usually a healthy system will show values of 0 or close to it all the way, yours was showing 0 all the time.

To me your system looks just fine, where did you get the information that your system is paging out?

Regards,

Jaime.

[roel_hawk]

Hi Jaime,

I'm running vmstat and swapinfo scripts in cron.

swap_info.sh
#--------------------------------------------
# Variable Definition
#--------------------------------------------
dat=`date "+%m/%d/%y %a %H:%M"`
filename=`date "+%m%d%y_%a.txt"`

#--------------------------------------------
# Gather Data
#--------------------------------------------
sw=`swapinfo -m|grep memory`

#--------------------------------------------
# Write Captured data to datafile
#--------------------------------------------
echo $dat $sw >> /tmp/Mon/data/swapinfo/swapinfo.txt



vm_stat.sh
#--------------------------------------------
# Variable Definition
#--------------------------------------------
dat=`date "+%m/%d/%y %a %H:%M"`
filename=`date "+%m%d%y_%a.txt"`

#--------------------------------------------
# Gather Data
#--------------------------------------------
sw=`vmstat`

#--------------------------------------------
# Write Captured data to datafile
#--------------------------------------------
echo $dat $sw|awk ' {print $1, $2, $3, $34, $35}' >> /tmp/Mon/data/vmstat/vmstat.txt

It bothered me when I get a 4% memory utilization and more than 20 page in and out. My understanding is paging happens only if the memory gets full. But in this case the memory is only 4%.

rgds,

Roel

[spex]

Hi Roel,

Check for memory-mapped files. When a memory-mapped file is posted, a page out will occur.

"Page in"'s can generally be ignored. They are quite common, and occur whenever a new process starts.

PCS

[Jaime Bolanos Rojas.]

Roel,

I just noticed one thing, I was about to ask you how do you know that your memory utilization is just 4%, it sound incredible low to me.

Then I notice that in swapinfo it says that the memory line is 4%, but memory here is not to be confused with physical memory or RAM, the memory line refers to pseudo-swap.

If you really want to know how much memory your system has free, you might want to check the memory line in the dmesg command or go to sam, performance monitors, system properties and memory.

I insist, your system looks fine to me for the moment.

Regards,

Jaime.