[mvapich-discuss] Bad performance of MVAPICH 1.8.1

[Devendar Bureddy]

Hi Stephan

I think the performance issue with mvapich2-1.9b using default RPUT
protocol could be because of registration cache entries ( default limit:
1024) ran out when more number of sends with different buffers in a loop.
Can you try with following mvapich2-1.9b run time parameters to increase
registration cache limit.

MV2_NDREG_ENTRIES_MAX
MV2_NDREG_ENTRIES

Set above two parameters to a same value ( 2048 or  4096 or 8192) and see
if that changes the behavior.

I'm not sure regarding the performance issue with 1.8.1.  Can you give more
details on configuration and run-time flags?  Can you check if expected
bandwidth is coming with osu_bw and osu_bibw benchmarks ?

-Devendar








On Fri, Apr 12, 2013 at 6:34 PM, Stephan Wolf <wolfst at in.tum.de> wrote:

> Hi,
>
> I had to switch to MVAPICH 1.9b in order to use the MPE environement
> for benchmarking. However I have expierenced significant reduction of
> the performance when using MVAPICH 1.9. It seems to be caused probably
> some bug in the RPUT protocol, because the R3 protocol works fine. I
> guess that the registration cache is not used.
>
> To illustrate my findings. Here is the pseudocode of my program:
> --------
> \\ Take time
> for(i to 20){
>   for(a to n) IRecv(rec_buffer[a])
>   for(a to n) ISend(send_buffer[a])
>   waitForAllRecv()
>   waitForAllSend()
> }
> \\ Plot time
> -------
> A diagram showing the effect can be found at:
> http://postimg.org/image/gddde14fr/
>
> What is the reason for that? Can I just stick to the R3 rendez-vous
> protocol, or does it has some disadvantage (like higher memory
> bandwidth consumption)
>
> Thanks
>
> Stephan
> _______________________________________________
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> mvapich-discuss at cse.ohio-state.edu
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>



-- 
Devendar
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