/proc/<pid>/smaps missing "Swap"

Rohit_4739 · 03-07-2013, 01:26 AM

Hi All,

I made a script few days back to find the process using the Swap in RHEL. I used the /proc/<pid>/smaps file and then extracting the Swap from it. Below is the script

Code:

for i in /proc/*/smaps ; do awk '/Swap/ {sum += $2}; END{ print FILENAME " Total: " sum}' $i; done | sort -nr -k 3

ANd it worked fine on most systems, but today i came across a system where the Swap was full so i ran the script but script didn't show my any results, so i digged into it and found that there is no Swap row in Smaps file. PLease see below

Quote:

# cat /proc/10686/smaps
2b6c5cc6b000-2b6c5ccc5000 r-xp 00000000 fd:01 164061 /usr/sbin/sshd
Size: 360 kB
Rss: 300 kB
Shared_Clean: 300 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
2b6c5cec5000-2b6c5cec8000 rw-p 0005a000 fd:01 164061 /usr/sbin/sshd
Size: 12 kB
Rss: 12 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 12 kB
2b6c5cec8000-2b6c5cecf000 rw-p 2b6c5cec8000 00:00 0
Size: 28 kB
Rss: 28 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 28 kB

As you see Swap is missing here. So can anyone please explain how and why Swap is missing here, and then from where Top actually picks up the processes's swap usage.

ANd below is a server where i see two additional rows

Quote:

cat /proc/30513/smaps
00400000-0b459000 r-xp 00000000 fd:09 269727 /u01/app/oracle/product/11.2.0.2/db_1/bin/oracle
Size: 180580 kB
Rss: 11972 kB
Shared_Clean: 11868 kB
Shared_Dirty: 0 kB
Private_Clean: 104 kB
Private_Dirty: 0 kB
Swap: 0 kB
Pss: 475 kB0b658000-0b820000 rwxp 0b058000 fd:09 269727 /u01/app/oracle/product/11.2.0.2/db_1/bin/oracle
Size: 1824 kB
Rss: 272 kB
Shared_Clean: 200 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 72 kB
Swap: 0 kB
Pss: 78 kB0b820000-0b86b000 rwxp 0b820000 00:00 0
Size: 300 kB
Rss: 204 kB
Shared_Clean: 8 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 196 kB
Swap: 0 kB
Pss: 196 kB

ANy help ideas,explaination would be highly appreciated.

syg00 · 03-07-2013, 02:12 AM

Looks like an old kernel - very old. What does "uname -a" show ?.

Rohit_4739 · 03-07-2013, 02:25 AM

Quote:

Originally Posted by syg00

Looks like an old kernel - very old. What does "uname -a" show ?.

Code:

root@dbsr0003:/root
# uname -r
2.6.18-92.el5
root@dbsr0003:/root

Its a RHEL5 machine so it is old but not very old

(just kidding). And secondly then how from where Top is picking up all the infomration. Below infomrmation is from a different machine with kernel having same major relaease that is 2.6,

Quote:

Pss: 40 kB
7fffcf1ab000-7fffcf1ad000 rw-p 7fffffffd000 00:00 0
Size: 8 kB
Rss: 4 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 4 kB
Swap: 0 kB
Pss: 4 kB
7fffcf1fc000-7fffcf200000 r-xp 7fffcf1fc000 00:00 0 [vdso]
Size: 16 kB
Rss: 4 kB
Shared_Clean: 4 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Swap: 0 kB
Pss: 0 kB
ffffffffff600000-ffffffffffe00000 ---p 00000000 00:00 0 [vsyscall]
Size: 8192 kB
Rss: 0 kB
Shared_Clean: 0 kB
Shared_Dirty: 0 kB
Private_Clean: 0 kB
Private_Dirty: 0 kB
Swap: 0 kB
Pss: 0 kB
root@xxxxx:/root
# uname -r
2.6.18-238.12.1.el5

So i am having hard time now understanding this why this weird behaviour ?

syg00 · 03-07-2013, 04:42 AM

I think that smaps support came in around 2.6.25/26 - quite a while ago.
As for top I think it calculates the swap when the smaps data isn't available - we've had several discussions here on LQ re whether it produced anything worth using.

Rohit_4739 · 03-07-2013, 04:44 AM

Quote:

Originally Posted by syg00

- we've had several discussions here on LQ re whether it produced anything worth using.

By the above statements do you mean Top or Smaps ??