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Date:      Fri, 10 Feb 95 9:02:53 MST
From:      terry@cs.weber.edu (Terry Lambert)
To:        wollman@halloran-eldar.lcs.mit.edu (Garrett Wollman)
Cc:        rminnich@mini.sarnoff.com, freebsd-questions@FreeBSD.org
Subject:   Re: enet throughput
Message-ID:  <9502101602.AA11205@cs.weber.edu>
In-Reply-To: <9502100339.AA02532@halloran-eldar.lcs.mit.edu> from "Garrett Wollman" at Feb 9, 95 10:39:30 pm

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> Two almost identical Pentium 60's running yesterday's kernel, one with
> a genuine SMC 8416 and one with a cheap 8216 clone:
> 
> ttcp-r: 16777216 bytes in 16.56 real seconds = 989.23 KB/sec +++
> ttcp-r: 16777216 bytes in 2.89 CPU seconds = 5678.54 KB/cpu sec
> ttcp-r: 11460 I/O calls, msec/call = 1.48, calls/sec = 691.93
> ttcp-r: 0.0user 2.8sys 0:16real 17% 52i+613d 138maxrss 0+2pf 6787+108csw
> 
> ttcp-t: 16777216 bytes in 16.67 real seconds = 983.04 KB/sec +++
> ttcp-t: 16777216 bytes in 3.65 CPU seconds = 4494.08 KB/cpu sec
> ttcp-t: 2048 I/O calls, msec/call = 8.33, calls/sec = 122.88
> ttcp-t: 0.0user 3.5sys 0:16real 21% 35i+440d 178maxrss 0+2pf 3969+41csw
> 
> This on a moderately loaded (~ 100 machines) Ethernet.

Hmmm... I think that ~5 times the number of I/O calls at ~1/6 the time
per call is an interesting statistic.  Seems to point right at the
problem spots... minus one piece of discriminating information -- was
this a UDP NFS problem or a TCP NFS problem?

Latency hits hard (per packet) for request/response, and ttcp does not
test for this, which yields one latency averaged across all packets.

NFS writes which are not async are very nearly request/response because
of the relative difference in time for window fill vs. doing a sync I/O
to a disk.


					Terry Lambert
					terry@cs.weber.edu
---
Any opinions in this posting are my own and not those of my present
or previous employers.



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