[mvapich-discuss] LiMIC2/KNEM

[Lockwood, Glenn]

Hello

The discussion raised a few thoughts/questions of my own:

On Jul 12, 2013, at 8:34 AM, Mark Dixon <m.c.dixon at leeds.ac.uk> wrote:
> ... it all depends on context, doesn't it? Some production clusters (of whatever size) can cope with vulnerabilities, some cannot. But is there a vulnerability here?

I think a large mitigating factor is that nodes in these large limic deployments are not shared; at worst, users would be able to shoot themselves in the foot or cause kernel panics.

> ...
>> Recent kernels provide support for kernel-based memory copy directly. One such support is called Cross Memory Attach (CMA). Thus, you do not need any separate Kernel module. MVAPICH2 1.9 provides support for CMA, in addition to LiMIC2.
> ...
> 
> Brilliant! Hadn't heard of that: I will certainly look out for it hitting our preferred server OS :)

It looks like CMA was included in 3.2 kernels.  From the MVAPICH2 release notes though, it wasn't clear to me: is there CMA support for collective operations, or just point-to-point?  And are there any performance comparison data for CMA vs. limic available to the public?

Thanks

Glenn

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Glenn K. Lockwood, Ph.D.
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glock at sdsc.edu
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