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

[Weikuan Yu]

Matthew Koop wrote:
> 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. Yes, that helps.

--Weikuan

> 
> 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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>