[mvapich-discuss] MVAPICH-1.0 Bandwidth drop with large window size

[Matthew Koop]

Weikuan,

Thanks for pointing this out. This is known issue that we are working on
addressing -- the queue length gets too long when the zero copy path is
not used. If you have applications where a large window will be used you
can increase the zero copy pool for the time being:

e.g.
../bin/mpirun_rsh -np 2 host1 host22 MV_UD_ZCOPY_QPS=128 ./bw

Thanks,

Matt

On Sun, 20 Jan 2008, Weikuan Yu wrote:

> Hi,
>
> I noticed a bandwidth problem with MVAPICH-1.0 UD implementation. Using
> osu_(bi)bw.c programs, if the window size is increased to 128 or above, the
> bandwidth can be quite low. I would assume there is a congestion in some
> queue processing.
>
> The difference should be readily reproducible. So I would not post the
> details numbers here. Let me know if you have some parameters to tune it up
> or need more info.
>
> --
> Weikuan Yu
> http://ft.ornl.gov/~wyu/
>
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