Re: [patch] acks delayed and then merged in data-segment sent a bitafter

Josip Loncaric (josip@icase.edu)
Tue, 02 Mar 1999 18:04:10 -0500


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Andrea Arcangeli wrote on March 2, 1999:
>
>[...]
>
> Here my current tree against 2.2.2, it does the thing I thought above:

I applied the suggested patch to Linux kernel 2.2.2 and measured
intermessage times while unidirectionally streaming 100,000 short
messages (1 byte each). The test was repeated with kernels 2.0.36 and
the unpatched 2.2.2, with the goal of comparing statistics of
intermessage times. Stream timings were collected separately on the
sender and the receiver, then merged and sorted to produce the attached
graph (Linux.gif, about 7KB):

RED: Linux kernel 2.0.36
GREEN: Linux kernel 2.2.2
BLUE: Linux kernel 2.2.2 with Andea's patch

The vertical axis shows intermessage time in seconds, with sorted rank
along the horizontal axis.

Both unpatched kernels stalled the data stream for 10 or 20 milliseconds
at a time, but the patch typically produced an improvement by a factor
of 20. This is very valuable in MPI-based multiprocessing applications,
and I intend to test this patch further.

Sincerely,
Josip

-- 
Dr. Josip Loncaric, Senior Staff Scientist        mailto:josip@icase.edu
ICASE, Mail Stop 403                        http://www.icase.edu/~josip/
NASA Langley Research Center             mailto:j.loncaric@larc.nasa.gov
Hampton, VA 23681-2199, USA    Tel. +1 757 864-2192  Fax +1 757 864-6134
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