How to read vmstat

[TSch]

Hi,

can anyone tell me how to read the vmstat output ?
What do all the numbers stand for ?
I'm especially interested in the following:

"r"
"b"
"avm"
"fre"

How can I tell if my machine only has a high workload but enough CPU time for all the processes currently running or if there are many processes that have to wait because there isn't enough free CPU time...

Thanks in advance !

Regards
T.Schmitt

 

[bjverzal]

The CPU stats are the last 4 columns.

us: Usable system time
sy: System (kernel) time
id: Idle
wa: Waiting I/O

$ man vmstat

will give you definitions on the column meanings.

Bill.

 

[aixqueen]

General tips....not by any means the do all end all.

cpu bound if vmstat sys and usr constantly => 80%
If run > 2.5 and CPU bound probably need another processor
If run queue <= 2.5 and CPU bound maybe a runaway process
disk bound if vmstat wa => 40%
Lot of PI and PO likely need more RAM
Iostat - lot of activity on one disk try to spread data over multiple drives

http://techsupport.services.ibm.com...mode=9&documents=090605226914708&database=aix

 

[vickersdc]

I agree completely with aixqueen, but I'd also like to add that I'd not worry about the value of avm (if I remember right - and I may be wrong here) but the algorithm used are brilliant and so the values are meaningless.

The value of fre is useful, if it constantly drops below about 120 (or the value of minperm - use vmtune to check) then it's a recipe for excessive paging.

The value of pi is also useful and a continual value over about 5 can also indicate excesive paging and a memory constrained system.

Hope it helps.
Dave V.

 

[ElgisRamon]

You must be checking the [tt]th|r[/tt] too, it must be under 5 always, that is an indicator of your machine having too much CPU work to do or too little processor for your chores...
I hope it works...
Unix was made by and for smart people.

 

[vickersdc]

I (sort of) take issue with the value of r ALWAYS below 5, as there's a formula somewhere (just wish I could find it!) that shows the 'max' level of r - which is dependant on, amongst other things, the number f processors in the system.

As soon as I find it I'll post it up, and then we can all pick holes in it ;-)

Cheers.
Dave V.