Check for thrashing

[Guy B. Purcell]

On Oct 4, 2005, at 19:26, Davy Durham wrote:

>  Does anyone know of a plugin that can check if a machine is  
> "thrashing" by which I mean it continues to swap and swap.. because  
> either there is too little ram, or too many processes running on  
> the box.

I think such a thing would be unnecessary, really:  if a box is  
thrashing (in the canonical sense of that word--something happens  
that causes it to have to work harder, which slows everything down so  
jobs pile up, causing it to have to work even harder, and so on in a  
catch-22 cycle), then the various services on it you're otherwise  
monitoring will time out because there aren't enough resources of one  
kind or another to handle the monitor requests.

>   I would think a vmstat command could tell you that, though it  
> would need a few seconds to determine.  And I'm not sure what  
> numbers would indicate what a bad amount would be.

The actual implementation of such a thing would need to be carefully  
crafted to work across multiple OSes.  IMHO, it's not worth the  
effort:  if a box truly is thrashing, you should know all about it  
from existing monitors.

-Guy




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