[httperf] Why does httperf take extra time even after completion

Prakhar Goyal prakhargoyal at cse.iitb.ac.in
Fri Jul 7 03:36:22 PDT 2006

Dear Sir,
Thankyou very much for your prompt reply. I am sorry that I could not
reply early as I was materialising the data.

Here is the report given by httperf in one of my expts, which involves the
performance analysis of web server:

____________Report Starts______________________________

httperf --server servername --port 80 --uri /model_prakhar/scene1.php
--rate 22 --num-conns 2000
httperf --client=0/1 --server=kahn.cse.iitb.ac.in --port=80
--uri=/model_prakhar/scene1.php --rate=22 --send-buffer=4096
--recv-buffer=16384 --num-conns=2000 --num-calls=1
Maximum connect burst length: 1

Total: connections 1799 requests 1627 replies 1623 test-duration 266.972 s

Connection rate: 6.7 conn/s (148.4 ms/conn, <=1022 concurrent connections)
Connection time [ms]: min 307.8 avg 53450.4 max 142786.6 median 36645.5
stddev 38681.8
Connection time [ms]: connect 51866.2
Connection length [replies/conn]: 1.000

Request rate: 6.1 req/s (164.1 ms/req)
Request size [B]: 94.0

Reply rate [replies/s]: min 0.0 avg 6.1 max 9.4 stddev 3.8 (53 samples)
Reply time [ms]: response 16056.6 transfer 0.0
Reply size [B]: header 206.0 content 504.0 footer 2.0 (total 712.0)
Reply status: 1xx=0 2xx=1623 3xx=0 4xx=0 5xx=0

CPU time [s]: user 5.44 system 261.53 (user 2.0% system 98.0% total 100.0%)
Net I/O: 4.8 KB/s (0.0*10^6 bps)

Errors: total 377 client-timo 0 socket-timo 172 connrefused 0 connreset 4
Errors: fd-unavail 201 addrunavail 0 ftab-full 0 other 0
________________Report Ends_____________________________

The client is a normal P4 machine having 2 CPUs.
The errors indicate that some connections failed.I had fixed the timeout
to be 100 secs.
The service time of the web server is 112 ms.
But after the web server finishes the handling requests,( ie, the machine
on which web server is deployed, shows 0% cpu usage), then also upto 1
minute(in this test case shown above), httperf continues running.

I think that this affects the request rate and the thruput too.
I know the 'request rate' shown by the htperf is diff from actual arrival
rate. I had read this in your mailing list archive. :)

Please reply to this matter soon as per your convenience.
I will be happy to provide you any other information required.

Waiting for the reply,

Thanks & Regards,
Prakhar Goyal.

> hi Prakhar
> without knowing anything about the test you were running, or about the
> configuration of the client, it is difficult to know what was happening.
> I expect that your test did not run cleanly in some way; e.g., some
> connections failed, or httperf had trouble getting file descriptors at
> some point during the test. However, without knowing more about the test
> or the httperf output from the test this is just speculation.
> Martin
> On Tue, 4 Jul 2006, Prakhar Goyal wrote:
>> Hello Sir,
>> The tool proved to be very helpful to me in my performance analysis of
>> Web
>> server.
>> In one expt, it displayed a test duration of 406 secs.
>> I ran 'top' and 'sar' on the web server, and also on the client machine,
>> on which httperf was running.
>> I found that when the web server has stopped utilizing cpu (ie, the test
>> is completed) , then also the httperf was running for some 6 -8 secs
>> with
>> cpu util of 100 % on the client machine.
>> Why does httperf take extra time ( in this case 6-8 secs) , even after
>> the
>> web server has stopped handling the requests..
>> Any kind of help will be most valauble.
>> Regards,
>> Prakhar,
>> IIT Bombay, India.
>> --
>> Prakhar Goyal
>> Computer Science & Engineering Dept.
>> IIT Bombay.
>> Homepage: http://www.cse.iitb.ac.in/~prakhargoyal
>> _______________________________________________
>> httperf mailing list
>> httperf at linux.hpl.hp.com
>> http://www.hpl.hp.com/hosted/linux/mail-archives/httperf/

Prakhar Goyal
Computer Science & Engineering Dept.
IIT Bombay.
Homepage: http://www.cse.iitb.ac.in/~prakhargoyal

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