[httperf] zero results in reply rate

[Roman Florea]

Hello,

while using httperf for benchmarking a very simple http server,
during some experiments it returns 0 values for the reply rates though  
all replies were received and no errors reported.
And it happens both on low values and high requested values.
Example output for requested conn rate of 360


httperf --hog -v  --server target --uri "/dump" --num-conn 1800  
--num-call 1 --timeout 5 --rate 360 --port 5000
httperf --verbose --hog --timeout=5 --client=0/, what are those 0  
samples., what are those 0 samples.1 --server=target --port=5000  
--uri=/dump --rate=360 --send-buffer=4096 --recv-buffer=16384  
--num-conns=1800 --num-calls=1
httperf: maximum number of open descriptors = 65000
Maximum connect burst length: 1

Total: connections 1800 requests 1800 replies 1800 test-duration 4.998 s

Connection rate: 360.1 conn/s (2.8 ms/conn, <=2 concurrent connections)
Connection time [ms]: min 0.4 avg 0.5 max 4.3 median 0.5 stddev 0.1
Connection time [ms]: connect 0.2
Connection length [replies/conn]: 1.000

Request rate: 360.1 req/s (2.8 ms/req)
Request size [B]: 84.0

Reply rate [replies/s]: min 0.0 avg 0.0 max 0.0 stddev 0.0 (0 samples)
Reply time [ms]: response 0.3 transfer 0.0
Reply size [B]: header 120.0 content 0.0 footer 0.0 (total 120.0)
Reply status: 1xx=0 2xx=1800 3xx=0 4xx=0 5xx=0

CPU time [s]: user 3.47 system 1.52 (user 69.5% system 30.4% total 99.9%)
Net I/O: 71.7 KB/s (0.6*10^6 bps)

Errors: total 0 client-timo 0 socket-timo 0 connrefused 0 connreset 0
Errors: fd-unavail 0 addrunavail 0 ftab-full 0 other 0


This happens on certain connection rates, and also happens for  
different server
and client OSes. The server code is using libevent and simply returns  
a 200 header for every connection it gets. The issues is seen on  
autobench progress:
dem_req_rate	req_rate_select	con_rate_select	min_rep_rate_select	avg_rep_rate_select	max_rep_rate_select	stddev_rep_rate_select	resp_time_selectnet_io_select	errors_select
32500	32267.4	322.7	32420	32420	32420	0	0.475	6428.2	0
35000	34694.3	346.8	34816.4	34816.4	34816.4	0	0.7375	6911.9	0
37500	37177.2	371.6	0	0	0	0	0.9	7406.4	0
40000	36438.7	364.2	31454.1	31454.1	31454.1	0	3.3625	7259.2	0
42500	23170.5	231.9	22745.4	22745.4	22745.4	0	25.75	4616.1	0

The other parameters seem fair, and error rate is always 0.
Could someone, please, explain what do these 0 mean and why this might happen.

Thank you.

Kind regards,
Roman Florea.