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Subject: Re: [OMPI users] Valgrind Warning
From: Gabriele Fatigati (g.fatigati_at_[hidden])
Date: 2008-12-15 06:37:50


Hi Jeff,
i recompiled libmthca with --with-valgrind flag, and modified
enviroment variables, but warnings doesnt' disappears..

2008/12/14 Jeff Squyres <jsquyres_at_[hidden]>:
> On Dec 14, 2008, at 8:21 AM, Gabriele Fatigati wrote:
>
>> i have a strage problems with OpenMPI 1.2.5 Intel Compiled when i
>> debug my code under Valgrind 3.3. In a very simple ping-pong MPI
>> application, i retrieve strange warnings about MPI Communications,
>> like MPI_Send,MPI_Recv. Valgrind tells me that there are uninitialized
>> values in send/recv buffers, but there are initialized, i'm absolutely
>> sure!
>>
>> There warnings are detected when my application runs over Infiniband
>> net,
>
> This is because IB uses memory that does not come from the memory allocator
> that Valgrind is aware of (e.g., it may be memory that was allocated by the
> kernel itself). Hence, since Valgrind is unaware of the memory, it thinks
> that its contents are undefined. As such, it's quite likely that you're
> seeing false positives.
>
> The memchecker support in the upcoming v1.3 series made quite a few
> advancements in the area of valgrind memory checking, and recent versions of
> libibverbs allow you to compile in valgrind extensions that tell valgrind
> "this memory is ok" (which prevents these false positives). I'm pretty sure
> that the OFED install does not enable these libibverbs valgrind extensions;
> you will likely need your own installation of libibverbs and your verbs
> plugin (libmthca for you, I think...?) that explicitly has the valgrind
> extensions enabled.
>
> --
> Jeff Squyres
> Cisco Systems
>
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>

-- 
Ing. Gabriele Fatigati
Parallel programmer
CINECA Systems & Tecnologies Department
Supercomputing Group
Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
www.cineca.it                    Tel:   +39 051 6171722
g.fatigati_at_[hidden]