[httperf] reply response time

Sylvain Geneves sylvain.geneves at inrialpes.fr
Fri Jun 10 01:06:19 PDT 2011


Hi,

I run httperf tests on multiple machines with no apparent problem. The throughput seems fine and the server behaves as expected when the rate increase.
But when it comes to analyse response times, I've got a problem : at low rate (from 10 to 30) some client nodes httperf show response and transfer times below 1msec, like this :

Reply time [ms]: response 0.1 transfer 0.1


I run my tests on a cluster over a LAN, where each node have 3 NICS : 2 ethernet 1Gbps, and 1 Myrinet 10Gbps emulating ethernet.
All these NICS are connected through switches, so my question is : how is that possible ?


If someone has some insight, I would really appreciate it.
Best regards,
Sylvain




for further details, here is the output of one of the clients :


Total: connections 9074 requests 66532 replies 66532 test-duration 471.350 s

Connection rate: 19.3 conn/s (51.9 ms/conn, <=192 concurrent connections)
Connection time [ms]: min 0.2 avg 8070.0 max 18122.8 median 7721.5 stddev 6129.8
Connection time [ms]: connect 0.2
Connection length [replies/conn]: 7.332

Request rate: 141.2 req/s (7.1 ms/req)
Request size [B]: 104.0

Reply rate [replies/s]: min 7.6 avg 141.6 max 163.8 stddev 22.9 (94 samples)
Reply time [ms]: response 0.1 transfer 0.1
Reply size [B]: header 63.0 content 14609.0 footer 0.0 (total 14672.0)
Reply status: 1xx=0 2xx=66532 3xx=0 4xx=0 5xx=0

CPU time [s]: user 122.56 system 347.76 (user 26.0% system 73.8% total 99.8%)
Net I/O: 2037.0 KB/s (16.7*10^6 bps)

Errors: total 0 client-timo 0 socket-timo 0 connrefused 0 connreset 0
Errors: fd-unavail 0 einval 0 addrunavail 0 ftab-full 0 other 0
Timeouts: total 0 class0=0 class1=0 class2=0 class3=0 class4=0 class5=0 class6=0 class7=0 class8=0 class9=0  

Session rate [sess/s]: min 4.20 avg 19.25 max 24.60 stddev 3.17 (9074/9074)
Session: avg 1.00 connections/session
Session lifetime [s]: 8.1
Session failtime [s]: 0.0
Session length histogram: 0 2676 0 0 0 571 587 625 557 592 606 556 557 585 575 587


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