[MPICH] any way to ask nemesis to turn-off and turn of active polling ?

[chong tan]

Yes, in a very subtle way which has major impact on performance.  I will try to decribe it a litle here:

system has 32G, total image 35G.  Load is a litle offbalance mathematically, 4X dual core, running 5 processes.
4 processes are the same size, each runs on a CPU.  the last process is very small, about10% of others, run
on a core of one of the CPU.  SO 1 CPU runs 2 procs: average (P1)one and light one (P2).

All proc do first MPI comm in a fixed algorithmic point.  The 'useful' image is about 29G at that point, and should
fit into the physical memory.  P2 get there in a heart beat, then others., followed by P1  which took another 60+ minutes
to get there.  If I combine P1 and P2 into 1 process, then I don;t no see this extra delay.

tan



----- Original Message ----
From: Darius Buntinas <buntinas at mcs.anl.gov>
To: chong tan <chong_guan_tan at yahoo.com>
Cc: mpich-discuss at mcs.anl.gov
Sent: Monday, December 17, 2007 8:02:17 AM
Subject: Re: [MPICH] any way to ask nemesis to turn-off and turn of active polling ?


No, there's no way to do that.  Even MPI_Barrier will do active polling.

Are you having issues where an MPI process that is waiting in a blocking 
call is taking CPU time away from other processes?

-d

On 12/14/2007 04:53 PM, chong tan wrote:
> My issue is like this :
>  
> among all the processess, some will get to the point of first MPI 
> communication points faster than
> than other.  Is there a way that I tell nemesis to start without doing 
> active polling, and then turn
> on active polling with some function ?
>  
> Or should I just use MPI_Barrier() on that ?
>  
> thanks
> tan
>  
> 
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