[X2Go-User] Graphical apps stalling in suspended session

[Matthew L. Dailey]

I tried reverting to nx-libs 3.5.0.30 and also 3.5.0.28. In both cases, the slowness while suspended was the same. So, it looks like this has been happening at least since November 2014. I’m not sure whether reverting further or reverting x2goserver to an earlier version would be helpful or not.

-Matt Dailey

> On Aug 15, 2015, at 8:57 AM, Matthew L. Dailey <Matthew.L.Dailey at Dartmouth.EDU> wrote:
> 
> Thanks you both for your responses.
> 
> In the case of X2Go, as I understand it, the processes that are running within the xfce session are not backgrounded when the X2Go client suspends the session. The idea is like screen - the processes continue to run normally and produce output to the X display (or virtual tty in the case of screen) - the user is just not getting updates since they’re not connected. From the perspective of the kernel, these processes should be scheduled just like any other active process.
> 
> The actual case where this was reported was a user running an app called Fluent which models flow and plots simulation convergence after each iteration. If we run this same simulation in batch mode without the graphical output, it continues to run normally even when the X2Go session is suspended.
> 
> In our case, we’ve been using X2Go for remote access to ten headless servers since January 2013, where our faculty, staff and students can do long-running simulations using engineering apps like Matlab, Fluent, etc. We’ve never tested this specific behavior, but it seems unlikely that this has been the case for the past 2 1/2 years without others reporting it. I’m going to test reverting the nx-libs upgrade from March (revert to 3.5.0.28-0~481~ubuntu14.04.1) to see if this makes any difference.
> 
> -Matt Dailey
> 
>> On Aug 14, 2015, at 10:38 PM, Robert Dinse <nanook at eskimo.com> wrote:
>> 
>> 
>>    There are process groups in Linux that might affect scheduling depending
>> on whether backgrounded or not.
>> 
>> -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
>> Eskimo North Linux Friendly Internet Access, Shell Accounts, and Hosting.
>>  Knowledgeable human assistance, not telephone trees or script readers.
>> See our web site: http://www.eskimo.com/ (206) 812-0051 or (800) 246-6874.
>> 
>> On Sat, 15 Aug 2015, Mihai Moldovan wrote:
>> 
>>> Date: Sat, 15 Aug 2015 03:17:14 +0200
>>> From: Mihai Moldovan <ionic at ionic.de>
>>> To: Robert Dinse <nanook at eskimo.com>,
>>>   Matthew L. Dailey <matthew.l.dailey at dartmouth.edu>
>>> Cc: "x2go-user at lists.x2go.org" <x2go-user at lists.x2go.org>
>>> Subject: Re: [X2Go-User] Graphical apps stalling in suspended session
>>> On 14.08.2015 11:01 PM, Robert Dinse wrote:
>>>>     I'm wondering if this is a bug or intentional?  It makes sense to me
>>>> to give more CPU time to interactive applications and lower CPU to those
>>>> where there isn't someone on a terminal waiting for a response.
>>> 
>>> True, and there's a new functionality in the yet unreleased 4.1.0.0 version of
>>> x2goserver called SuperRenicer (disabled by default) that can be used to renice
>>> suspended sessions so they run with lower priority.
>>> 
>>> Even then, though, the execution should not be slower than when attached, unless
>>> the CPU is well-loaded in the first place.
>>> 
>>> There's no functionality in 4.0.1.x that would actively slow down applications
>>> (most likely draw calls - not applications in general) when suspended.
>>> 
>>> 
>>> 
>>> Mihai
>>> 
>>> 
>>> 
>