[hobbit] Out of range memory report

[Henrik Stoerner]

On Thu, Aug 03, 2006 at 11:37:02AM +0100, Colin Spargo wrote:
> I got this in the "memory" column for a Solaris 8 host this morning, which 
> caused it to go red (even though i have the threshold set to 101).
> 
>  Thu Aug 3 09:11:17 BST 2006 - Memory CRITICAL
>    Memory              Used       Total  Percentage
> red Physical     4294955003M     131072M 4294967287%
> green Swap              40973M     144024M         28%
> 
> 
> That physical memory calculation is obviously incorrect!

Yep, but the data it got were weird. Colin sent me some additional
data from the client message. The interesting bits are here:

The Solaris prtconf command is used to determine the amount of RAM
in the box. Here is says:

[prtconf]
System Configuration:  Sun Microsystems  sun4u
Memory size: 131072 Megabytes

So this box has 131072 MB. (128 GB - a lot, I might add. Is this really
true?)

The command "vmstat 1 2|tail -1" is used to grab the current memory
usage:

[memory]
0 0 0 211046168 146806184 744 6249 0 0 0 0 0 0 0 0  0 2692 436955 11454 8 6 86

Column 5 is the "free memory" column in KB, here: 146806184 KB. Divide
by 1024 to get MB, and it gives 143365 MB free.

Now ... how can a box with 131072 MB RAM end up with 143365 MB free ?
That's almost 12 GB more than what is physically installed in the box.

Hobbit then gets a negative value for the amount of memory used, and
because it is then used in a calculation with some unsigned variables
it blows up and comes up with this hilarious value of the amount of
memory used.


Now, I'll admit that Hobbit should probably do a sanity check on the
data so it doesn't trigger alerts in these circumstances. But the core
problem is that your box is reporting some weird data.


Regards,
Henrik