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Curtailing long running VNC sessions on nemo due to heavy load |
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Written by Janaka Jayawardena
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Monday, 24 January 2011 |
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At 6pm, on
a daily basis, any VNC session on nemo that has been running for longer than 12
hours will be terminated. A message will be sent to these sessions
before the termination. This is an effort to keep nemo usable for active users due to heavy loading.
The Solaris host nemo.ece.pdx.edu is the major ECE compute workhorse for
that platform and provides access to a wide arrays of tools from Mentor
and Cadence (among other things). It is accessed directly from the
SunRays in the VLSI Lab and also via remote access. The latter method
is becoming increasingly popular.
The load on nemo in recent terms has been particularly heavy. The tools
being used are very aggressive in terms of CPU, memory and process
table slots. We are seeing periods where nemo is coming to a crawl.
In an effort to keep nemo usable for active users, we are going to
institute a policy of terminating long running VNC sessions. At 6pm, on
a daily basis, any VNC session that has been running for longer than 12
hours will be terminated. A message will be sent to these sessions
before the termination.
Users running VNC are encouraged to treat their sessions as solely for
active and interactive use only and shut them down (not just disconnect)
when they are done.
The goal of this restriction is to keep nemo as usable as possible for
the students working on class assignments. If a long running sim is
desired, that will need to be arranged with an understanding of its
impact on assigned classwork.
While the ability to keep a persistent session that a remote user can
return to is useful, the load from these sessions (which are seldom
fully idle due to the noisy nature of modern X desktop trappings) are
contributing to the severe loading on this host.
We have already set up a wrapper around Xvnc so that multiple
invocations are harder to do accidentally. We will also be policing
runaways more aggressively - user processes with no connection to a
login or SunRay/VNC session.
SunRay users' sessions should not be affected by this. It will mainly
hit people who keep a VNC session running longer than 12 hours.
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Last Updated ( Monday, 24 January 2011 )
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