Check for thrashing

Terry td3201 at gmail.com
Wed Oct 5 07:49:26 CEST 2005


Sar tools might be more useful for you.

On 10/5/05, Davy Durham <pubaddr2 at davyandbeth.com> wrote:
> 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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>
>
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