[mpich-discuss] Hydra binding questions

[Pavan Balaji]

On 08/01/2011 06:38 PM, Jain, Rohit wrote:
> 1)Is there any debug output by Hydra, which tells particular
> core/processor binding (core numbers) associated with a process? We can
> use this info to see variation of binding methods on different
> architectures.

Yes, good point. We don't print out the binding information in the 
verbose output currently. I'll add that in. Can you add a ticket for 
this? https://trac.mcs.anl.gov/projects/mpich2/newticket

> 2)We expected cpu:sockets and cache:l3 binding to behave same on an AMD
> box due to its layout (2 processors with 6 cores each). But, there is
> difference in performance of about 10%. Is that expected? Again, any
> information on binding will help, currently it is black box for us of
> what Hydra does.

Once I add print out the binding, you'll know what binding it's using. 
That might help debug this.

> 3)While running on AMD Opteron machine, I monitored ‘top’ as application
> was running. I found that processes are shuffling between different
> cores during the run. Is that expected, as processes are bind to a
> particular core? I also noticed it on Intel machine, but happening less
> frequently.

That shouldn't happen.

> 4)We currently use numactl/taskset to set affinity with mpd. Does hydra
> allow specifying affinity with numactl/taskset, instead of -binding?

Yes, of course. numactl/taskset are independent of the process manager. 
You can use them with any process manager.

> 5)What parameter does hydra read from machine to determines binding?
> /proc/cpuinfo or more?

It uses hwloc to get the process topology information.

  -- Pavan

-- 
Pavan Balaji
http://www.mcs.anl.gov/~balaji