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Re: [tcpm] TCP tuning

rick jones <perfgeek@mac.com> Thu, 04 February 2010 06:08 UTC

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From: rick jones <perfgeek@mac.com>
To: rick jones <perfgeek@mac.com>
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Date: Wed, 03 Feb 2010 22:09:00 -0800
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Cc: tcpm@ietf.org, "SCHARF, Michael" <Michael.Scharf@alcatel-lucent.com>, Joe Touch <touch@ISI.EDU>
Subject: Re: [tcpm] TCP tuning
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On Feb 3, 2010, at 9:41 PM, rick jones wrote:
> PS - I suppose if I'd been thinking more clearly, I'd have also  
> included --enable-historgram in the ./configure command and been  
> able to give a histogram of the response times (adding a -v 2 option  
> to the global command line options), but I suppose that can be  
> guesstimated from the traces.

Ok, so perhaps I like running netperf too much :)  Here then are the  
application-level measured response times.  The first netperf is with  
tcp_slow_start_after_idle = 0, the second with it set to 1, I'll leave- 
out the rest of the netperf output as it is repetitive:

tcp_slow_start_after_idle = 0 on server:

Histogram of request/response times
UNIT_USEC     :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
TEN_USEC      :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
HUNDRED_USEC  :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
UNIT_MSEC     :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
TEN_MSEC      :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
HUNDRED_MSEC  :    0:  294:    4:    0:    2:    0:    0:    0:     
0:    0
UNIT_SEC      :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
TEN_SEC       :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
 >100_SECS: 0
HIST_TOTAL:      300

That means 294 times 100ms <= responsetime < 200ms, 4 times it was  
200ms <= responsetime < 300ms etc etc.

tcp_slow_start_after_idle = 1 on server:

UNIT_USEC     :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
TEN_USEC      :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
HUNDRED_USEC  :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
UNIT_MSEC     :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
TEN_MSEC      :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
HUNDRED_MSEC  :    0:    0:    0:  290:   10:    0:    0:    0:     
0:    0
UNIT_SEC      :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
TEN_SEC       :    0:    0:    0:    0:    0:    0:    0:    0:     
0:    0
 >100_SECS: 0
HIST_TOTAL:      300

Now it was 290 with 300ms <= responsetime < 400ms

Just as a refresher, the request size was 128 bytes, the response size  
16384.

The ICMP Echo RTT is ~120 ms between my home system and netperf.org:

--- netperf.org ping statistics ---
10 packets transmitted, 10 packets received, 0% packet loss
round-trip min/avg/max/stddev = 119.523/120.410/121.248/0.493 ms

rick jones
Wisdom teeth are impacted, people are affected by the effects of events

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