Check for thrashing

[Davy Durham]

Timothy O'Hare wrote:

> You could monitor the CPU load and swap space usage?
>
Yeah, but my question was what values from vmstat would mean that it's 
thrashing.. a plugin would seem simple to write to check that

> Guy B. Purcell wrote:
>
>>
>> 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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>
>
>
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