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SubjectRe: Detecting threads vs processes with ps or /proc
FromGilad Ben-Yossef <>
Date08 Dec 2002 14:24:42 +0200
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On Fri, 2002-12-06 at 17:24, Nick LeRoy wrote:


Our software (Condor) and some related software (Globus) is running on a number of systems around the world. Condor attempts to monitor the RAM usage of it's "user" (maybe "client" is a better word here) processes. If the client forks, we need to monitor the client and all of it's children, which really isn't difficult. The _problem_ is that if the client creates threads, it's impossible, from what we can tell, to tell the difference between separate threads and processes.

So my question, I guess, is this. How can you tell, from user space, whether a group of processes are related as threads or through a "normal" child / parent relationship? The systems that we're running on currently are 2.2.19 and 2.4.18/19.

There is another approach save for the one already discussed here, which I have no idea how applicable it is in your case, but will produce 100% reliable results without additional kernel support - track the processes forks.

There are several ways you can go about it - there's the expensive (in terms of CPU cycles) approach of using ptrace(2), the relativly painless way of overriding the "default" calls to fork and friends via ld.so(8) magical LD_PRELOAD that nevertheless requires you control the execution of the "client" programs and even using a system call tracking module such as syscall-tracker (http://syscalltrack.sf.net) which might not be quite ready for use on a production system as of yet.
Hope this helps,
Gilad

-- 
 Gilad Ben-Yossef <gilad@benyossef.com> 
 http://benyossef.com 
 "Denial really is a river in Eygept."
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