[Spread-users] sporadic latencies with SP_receive

[Johannes Wienke]

Hey again,

sorry for bumping, but are there any ideas how and why this happens? It
really decreases our performance right now.

Regards,
Johannes

On 07/25/2011 01:47 PM, Johannes Wienke wrote:
> Dear all,
> 
> we encountered some latency issues in our applications using spread.
> Today we tried to isolate the problem and came up with a test program
> that demonstrates the behavior.
> 
> Generally, the observation is that in a threaded setup, using local
> communication, and a small sleep between calls to SP_receive, these
> receive calls sometimes take up to 100 ms, e.g. generating this log:
> 
> receive took 55 us
> receive took 68 us
> receive took 97071 us
> receive took 54 us
> receive took 67 us
> receive took 97060 us
> receive took 54 us
> receive took 68 us
> receive took 97086 us
> receive took 56 us
> receive took 69 us
> receive took 97091 us
> receive took 56 us
> receive took 67 us
> receive took 97071 us
> 
> The attached program exactly produces this output. Please note that this
> only happens if the sleep call is present in line 108.
> 
> We have also verified that this is not related to the architecture we
> are running on (Linux 32 and 64 bit), nevertheless we got a stack
> corruption on 32 bit in the sender thread with a privateGroup array only
> MAX_PRIVATE_NAME characters long. Thus the increased size. Is this also
> a known problem?
> 
> We would be happy to get some insights or fixes in how to prevent this
> issue. In a real application the sleep is usually not required to
> trigger the problem as the receiving thread is still doing other things
> in its loop.
> 
> Regards,
> Johannes
> 
> 
> 
> _______________________________________________
> Spread-users mailing list
> Spread-users at lists.spread.org
> http://lists.spread.org/mailman/listinfo/spread-users


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