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Re: [Xen-devel] MPI benchmark performance gap between native linux anddo

To: "Santos, Jose Renato G (Jose Renato Santos)" <joserenato.santos@xxxxxx>
Subject: Re: [Xen-devel] MPI benchmark performance gap between native linux anddomU
From: xuehai zhang <hai@xxxxxxxxxxxxxxx>
Date: Tue, 05 Apr 2005 00:27:22 -0500
Cc: "Turner, Yoshio" <yoshio_turner@xxxxxx>, Aravind Menon <aravind.menon@xxxxxxx>, Xen-devel@xxxxxxxxxxxxxxxxxxx, G John Janakiraman <john@xxxxxxxxxxxxxxxxxxx>
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Jose,

Thank you so much for your valueable information.

  I guess I overlooked the rates you reported in your post.
  Looking now at your rates carefully I got somewhat confused. When you
say MB/sec do you mean Megabyte/sec or Migabit/sec?

It is Megabyte/sec (2^20 bytes)

In any case these
are much lower rates than in our case (we were using a gigabit network).
Now, I am starting to think that your problem might be different than
ours, but it does not hurt to try changing the advertised window, just
in case.

I will try your suggestion and sent out update tomorrow morning.

  Also, the numbers your report are inconsistent. You mention that your
network is 10 MB/s, and that native linux achieve 14.9 MB/s. How is it
possible to achieve a throughput higher than the network bandwidth?
Could you please clarify?

Yes, it is a little confusing. It is due to the caculation of SendRecv's throughput. If you take a look at the PMB user manual (following the link in my previous email), the throughput is defined as 2X/1.048567/time (time is latency). So, it is a weighted throughput and could go beyond 10MB/s, which is the max bandwidth of the network.

Thanks.

Xuehai

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