[Zope-dev] Increased system CPU cycles under heavy load?

[Erik Stephens]

Hello all,

I apologize if this might be more appropriate for a Linux list.  From
our time-series graphs, we are noticing that the percentage of CPU
cycles spent on 'system' tasks grows considerably under heavy load. 
Does anyone know what kinds of operations fall under 'system'?  Task
switching, paging, these kinds of things?

When load is light, it appears that the same 1 or 2 Zope threads will
handle the requests.  As load increases, then more threads get into the
mix.  How likely is it that this increase in 'system' CPU cycles is
stemming from having to switch between the Zope threads?  Perhaps Zope
goes into a near dead-lock state and starts to spend a bunch of time
waiting for other threads to release a lock?  The reason I mention this
is that we don't notice the increased amount of 'system' CPU when the
load increases on other servers (Apache, MySQL) on other machines.

System info: Zope 2.1.6, Redhat 6.2, PC arch

Thanks,
Erik