[httperf] output - num-calls and num-conns difference

Tim Terrill TTerrill at synacor.com
Wed Feb 26 06:04:58 PST 2014

I believe that there is another factor here, your wlog file.  I'm not totally sure the interaction, but it seems like you might have only 2 URIs in that file, so each connection will use that file to issue requests and since you said "n" as the first option, and it appears that you only have 2 lines in the file, each connection will issue two requests, and as Martin said if your server doesn't support persistent connections you don't get a reply to the second request…

I believe that httperf uses that file for the requests when that option "wlog" is present, the num-calls parameter is rendered inactive, but I'm not sure…

Can U tell us what is in your .txt file?


From: <Arlitt>, Martin <martin.arlitt at hp.com<mailto:martin.arlitt at hp.com>>
Date: Wednesday, February 26, 2014 8:26 AM
To: 'neubyr' <neubyr at gmail.com<mailto:neubyr at gmail.com>>, "httperf at linux.hpl.hp.com<mailto:httperf at linux.hpl.hp.com>" <httperf at linux.hpl.hp.com<mailto:httperf at linux.hpl.hp.com>>
Subject: RE: [httperf] output - num-calls and num-conns difference


The web server you are testing does not appear to support persistent connections. That is why in your first case the output says “10 connections” were created, “20 requests” were made but only “10 replies” were received, and in your second case “4 connections” were created, “8 requests” were made and only “4 replies” were received.

What is happening is httperf establishes a connection with the server, issues its first call on that connection, receives a reply to that call, then quickly issues its second call, before httperf receives the server’s indication that it wants to close the connection (which the server may make via a TCP FIN packet that httperf won’t see directly rather than an HTTP header that httperf would see directly). You may have to use a tool like tcpdump to monitor the network traffic to see this behavior. If the server is attempting to close the connection via an HTTP header, then would could also try the –print-request and –print-reply options in httperf to see what is going on.


From: httperf-bounces at linux.hpl.hp.com<mailto:httperf-bounces at linux.hpl.hp.com> [mailto:httperf-bounces at linux.hpl.hp.com] On Behalf Of neubyr
Sent: Tuesday, February 25, 2014 11:42 PM
To: httperf at linux.hpl.hp.com<mailto:httperf at linux.hpl.hp.com>
Subject: [httperf] output - num-calls and num-conns difference

When I run httperf with following options, the output is easy to understand.

Options: Make total 10 connections (num-conns) at rate of 10 (rate) connections/second with 2 request calls per connection (num-calls).
Output: 10 connections with 20 request calls

    httperf -v --server www.example.com<https://www.example.com> --wlog=n,$HOME/tmp/reqs.txt_httperf --rate=10 --num-conns=10 --num-calls=2 --hog
    Total: connections 10 requests 20 replies 10 test-duration 1.575 s

However, when I use following options, httperf output, output is confusing.
Options: Make total 4 connections (num-conns) at rate of 10 (rate) connections/second with 6 request calls per connection (num-calls).

    httperf -v --server www.example.com<https://www.example.com> --wlog=n,$HOME/tmp/reqs.txt_httperf --rate=10 --num-conns=4 --num-calls=6 --hog
    Total: connections 4 requests 8 replies 4 test-duration 0.455 s

It seems like when num-calls is greater than num-conns, number of requests made are 2*num-conns.

I am not following why num-calls be greater than num-conns. Am I missing anything?

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