[Mauiusers] insufficient idle procs available ?

Itay M itaym.tau at gmail.com
Thu Jan 31 20:01:26 MST 2008


Well, you definitley came up with something interesting. The
NODEAVAILABILITYPOLICY looks as if it should help me to resolve this issue
(but currently it didn't...yet).

I've made the following tests trying to figure what's behind the scenes of
the cluster:

1. I listed all the nodes that diagnose -n says: "has more processors
utilized than dedicated"
2. Then I submitted several very short jobs (2 minutes) and designated each
one of them to each one of the nodes listed above. I used the -l
host={nodename} -l walltime=00:00:02 (The walltime time purpose is to make
sure MAUI will not activate any reservation policies on the jobs (In fact
the cluster had many free CPUs at the time I made the test, so no
reservations are expected)). I expected the jobs *not* to go in to R state,
because each and every job was targeted to a node that "has more processors
utilized than dedicated" .
3. Indeed that's what happend! None of the jobs went from Q state to R
state. They have been waiting there for very long time (hours).
4. I then checked the load average on each of the nodes listed above, and I
indeed found that their load average is higher than their configured
resources. For example, if the 'nodes' file says 'node22 np=4' , I checked
it's load average at the time it had the "has more processors utilized than
dedicated" . I found that though this node runs only 2 jobs at the moment,
the load average is above it (about 2.70). I expect this node to run 4 jobs
at the same time.

> Are these2 jobs multithreaded? Is the load ~4 while it should be ~2?
I'm not sure if they are multithreaded (needs further checking with the
developers) -  but you're right. The load should be no more than 2 for 2
jobs, but infact its >2 . The jobs are C++ compiled with g++ compiler. Maybe
a compilation switch will help with reducing the load average to 1 per job?

I then moved to the next step, and set the NODEAVAILABILITYPOLICY to
UTILIZED. The showconfig command now says:
NODEAVAILABILITYPOLICY[0]         UTILIZED:[DEFAULT]
As this didn't make the jobs run, perhaps it's a matter of another tweak in
the NODEAVAILABILTY policy?

And yet another thing about the diagnose -j output : I'm not sure if and how
should I treat the  'WARNING:  job '{job_id}' utilizes more memory than
dedicated (xxxx > 512) ' .  A vmstat test shows that indeed jobs are heavily
swapping on the node.

Thanks,
Itay.


On Jan 30, 2008 12:26 AM, Jan Ploski <Jan.Ploski at offis.de> wrote:

>
> Jan Ploski
>
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