[mvapich-discuss] mvapich2-0.9.8-branch question

[Kanoj Sarcar]

--- Sundeep Narravula <narravul at cse.ohio-state.edu>
wrote:

> Kanoj,
> 
> > Yes, the rnic I am working with can be put into a
> mode
> > to guarantee in-order placement.
> 
> This is good for RDMA_FAST_PATH.
> 
> > I think a specifiable environment variable should
> be
> > able to handle this case correctly, no?
> 
> We will be providing an option to enable
> RDMA_FAST_PATH with a specifiable
> environment variable. This will be in the SVN in the
> next 1-2 days.

Thanks; any chance this can get picked into ofed 1.2?

> 
> > In general, are there any online documents
> describing
> > internals of mvapich/iwarp and the various
> settable
> > parameters etc? For example, if a newbie wanted to
> > understand the iwarp primitives used in a
> benchmark
> > program (say one of the osu_benchmarks), how would
> he
> > go about that?
> 
> All the information regarding the adjustable
> parameters of MVAPICH2 are
> available from the MVAPICH2 user-guide.
> 
>
http://nowlab.cse.ohio-state.edu/projects/mpi-iba/user_guide.html
>
http://nowlab.cse.ohio-state.edu/projects/mpi-iba/download-mvapich2/mvapich2_user_guide.html
>

Okay, thanks, I will look these over.

Kanoj
 
> Cheers,
>   --Sundeep.
> 
> >
> > Thanks.
> >
> > Kanoj
> >
> > --- Sundeep Narravula
> <narravul at cse.ohio-state.edu>
> > wrote:
> >
> > > Hi Kanoj,
> > >
> > >   The RDMA_FAST_PATH that we use in mvapich2
> > > involves polling on the last
> > > byte of an expected message to flag message
> > > completions on the remote
> > > side. Since this is not guaranteed by iWARP we
> have
> > > disabled this
> > > by default for the iWARP mode.
> > >
> > > Does the RNIC you use guarantee inorder
> placement of
> > > RDMA bytes into the
> > > remote buffer? or guarantee that the last byte
> will
> > > be placed last into
> > > the user buffer?
> > >
> > > Regards,
> > >   --Sundeep.
> > >
> > >
> > > On Wed, 14 Feb 2007, Kanoj Sarcar wrote:
> > >
> > > > Hello all,
> > > >
> > > > I am a mpi/mvapich newbie looking at iwarp
> support
> > > in
> > > > mvapich2.
> > > >
> > > > Between 0.9.8 release and branch, in procedure
> > > > rdma_get_control_parameters() in file
> > > >
> > >
> >
>
src/mpid/osu_ch3/channels/mrail/src/gen2/ibv_param.c,
> > > > I see a difference that I am trying to
> understand.
> > > >
> > > > In the release version, the code was:
> > > >
> > > >    if ((value =
> > > getenv("MV2_DISABLE_RDMA_FAST_PATH"))
> > > > != NULL) {
> > > >         proc->has_adaptive_fast_path = 0;
> > > >         rdma_polling_set_limit       = 0;
> > > >     } else {
> > > >         proc->has_adaptive_fast_path = 1;
> > > >     }
> > > >
> > > > but this got changed in the branch version to
> also
> > > > turn off adaptive fast path in case of iwarp.
> > > >
> > > > I am curious about the rationale for this
> change.
> > > Is
> > > > this to mostly support amasso card that
> (AFAIK)
> > > does
> > > > not have user mode fastpath support? Or is
> there
> > > some
> > > > architectural issue in current mvapich2 that
> > > requires
> > > > turning off fastpath on iwarp rnics?
> > > >
> > > > Thanks.
> > > >
> > > > Kanoj
> > > >
> > > > PS: please cc me on responses, I am not
> subscribed
> > > to
> > > > the list
> > > >
> > > >
> > > >
> > > >
> > >
> >
>
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