No swapping but high page out rate ???

[Mike Boswell_1]

Can someone help me shed some light on this? No swap space used but a high rate of pgpgout/s. This is a Tomcat server hosting ~ 20 apps.

Thanks,
Mike

# sar -B 2 5
Linux 2.4.21-53.ELsmp (cimprd1) 09/14/2010

09:55:09 AM pgpgin/s pgpgout/s fault/s majflt/s
09:55:11 AM 0.00 122.61 0.00 0.00
09:55:13 AM 0.00 166.00 0.00 0.00
09:55:15 AM 0.00 156.00 0.00 0.00
09:55:17 AM 0.00 212.00 0.00 0.00
09:55:19 AM 0.00 214.00 0.00 0.00
Average: 0.00 174.17 0.00 0.00

[root@cimprd1 logs]# vmstat 2 5
procs memory swap io system cpu
r b swpd free buff cache si so bi bo in cs us sy id wa
0 0 0 373184 305064 3910420 0 0 16 1 19 11 2 1 22 0
1 0 0 373716 305064 3910424 0 0 0 172 234 718 1 4 96 0
0 0 0 372508 305068 3910452 0 0 0 698 464 1014 1 4 95 0
0 0 0 372504 305068 3910468 0 0 0 182 1006 1489 3 0 97 0
0 0 0 372436 305084 3910696 0 0 0 578 1533 2464 9 2 89 0

# free
total used free shared buffers cached
Mem: 8198088 7821592 376496 0 304928 3906248
-/+ buffers/cache: 3610416 4587672
Swap: 13197304 0 13197304

[Ivan Ferreira]

The pgpgouts/s from sar is equivalent to io bo from vmstat.

From the man page of vmstat:

bo: Blocks sent to a block device (blocks/s).
so: Amount of memory swapped to disk (/s).

So, you are not having page outs related to memory (swap/so).

[Mike Boswell_1]

Ivan thanks for the reply. Do you know any way for me to isolate the major contributors for the BO. Filesystem, files, process, user, ect. Could this be high levels of logging in Tomcat?

[Ivan Ferreira]

Probably iotop can help you:

http://guichaz.free.fr/iotop/