[Mauiusers] Nodes have 8gb memory, maui shows less

Michel Béland michel.beland at rqchp.qc.ca
Wed Jul 28 09:12:39 MDT 2010


Hello,

> I'm running torque 2.3.7 and maui 3.2.6.
> Everything appears to working fine. I can submit jobs and they run 
> successfully.
> I'll dump my configs, if required.
> 
> I've got this weird problem where my nodes have 8GB of RAM, however when 
> I submit jobs to torque that request mem=8gb, they are never started by 
> maui. If I was to submit the same job to torque and request mem=7900mb, 
> maui will then start the job.

This is perfectly normal.

> Pbsnodes in torque shows 8GB of memory:
> 
>       state = free
>       np = 8
>       properties = corvus
>       ntype = cluster
>       status = opsys=linux,uname=Linux 2.6.16.46-0.12-smp #1 SMP Thu May 
> 17 14:00:09 UTC 2007 x86_64,sessions=? 0,nsessions=? 
> 0,nusers=0,idletime=0,totmem=24563472kb,availmem=24433724kb,physmem=8179480kb,ncpus=8,loadave=0.00,netload=28007785,state=free,jobs=,varattr=,rectime=1280298000


No, this is not 8 GB, but 8179480 KB, which is *not* the same. As 1 MB = 
1024 KB and 1 GB = 1024 KB, this means that 8179480 KB is 7987,7734 MB 
and is also 7,80056 GB. You have to remember that the OS takes some 
memory that is not available to programs. If you type the command "free" 
on this compute node, you will see that you do not have the full 8 GB 
available.

> But when I run the maui command checknode it shows:
> 
> checking node
> State:      Idle  (in current state for 00:10:08)
> Configured Resources: PROCS: 8  MEM: 7987M  SWAP: 23G  DISK: 1M

So Maui shows the same memory as pbsnodes, but rounded down to integer 
megabytes.

> Does anyone have an idea why maui seems to show slightly less than 8GB 
> or rather 8000mb?
> Is this a problem with maui, or should I be looking at torque instead?

That is how Linux works (and probably other Unix systems too).

-- 
Michel Béland, analyste en calcul scientifique
michel.beland at rqchp.qc.ca
bureau S-250, pavillon Roger-Gaudry (principal), Université de Montréal
téléphone : 514 343-6111 poste 3892     télécopieur : 514 343-2155
RQCHP (Réseau québécois de calcul de haute performance)  www.rqchp.ca
Calcul Canada (computecanada.org)


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