[mvapich-discuss] LiMIC2/KNEM

[Dhabaleswar Panda]

Hi,

Thanks for your note. Please find my response in-line.

> I'm looking at trying to give MPI performance a boost with one of the 
> kernel-assisted memory copy modules. I see there are a few of them, including 
> LiMIC2 and KNEM.
>
> The website for LiMIC2, http://sslab.konkuk.ac.kr/, isn't responding but 
> MVAPICH2 seems to be the biggest user of the software (according to Google), 
> so I'm posting my question here.

Compared to the original version (as indicated in the above website), 
there have been many enhancements in LiMIC2 being used in the latest 
MVAPICH2 version.

>
> I've read about a few security concerns about LiMIC2 dotted around the net, 
> but not found any official documentation to confirm/refute that an attacker 
> can use it to read any memory they like.
>
> Are the concerns real? If so:

Many production clusters (including the very large ones at TACC) have been 
using MVAPICH2 with LiMIC2 for the last several years on a daily-basis. 
Thus, these concerns do not appear to be real.

> * Are there any plans to address them?
>
> * Is KNEM supported with MVAPICH2 as an alternative? (I see it wasn't in 
> 2011)

Not in the default OFA-IB-CH3/OFA-iWARP-CH3/OFA-RoCE-CH3 channel.

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. Please take a look at the following section of the 
MVAPICH2 user guide regarding how to configure MVAPICH2 to work with CMA 
support get the performance boost.

http://mvapich.cse.ohio-state.edu/support/user_guide_mvapich2-1.9.html#x1-110004.4

Thanks,

DK

> Thanks,
>
> Mark
> -- 
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