[mvapich-discuss] viadev_max_rdma_size

[Matthew Koop]

Pasha,

You are correct about the purpose of the parameter. The 1MB value was
tuned to allow good performance with previous generation IB firmware and
hardware that had a degradation of RDMA write performance above 1MB.

Given that moving the maxiumum message size to 4MB no longer has any
performance issues we've adjusted the default parameters in the trunk of
our SVN.

Thanks for your suggestion,

Matthew Koop
-
Network-Based Computing Laboratory
Ohio State University



On Wed, 28 Jun 2006, Pavel Shamis (Pasha) wrote:

> Hi,
> As I understand the parameter limits maximal rdma(PUT) message size for
> rendezvous protocol (viadev_rendezvous_push). The default value of it is
> 1Mb. I did some performance testing (micro-benchmarks) on DDR/SDR
> platforms and I figure our that the default value is not optimal. It
> looks that for the micro-benchmarks the 4M is best value.
>
> Thanks,
> Pavel Shamis (Pasha)
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