Changes between Version 27 and Version 28 of PerformanceTesting
- Timestamp:
- 11/11/11 11:06:50 (12 years ago)
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PerformanceTesting
v27 v28 352 352 == Head/tail effect == 353 353 354 When the number of clients was increased,the incapability of the server processes - especially iperf - to establish new connections quickly started to show with as few as 20 clients. This was clearly visible when looking at server-side iperf output: clients connected with delay of several seconds. This had two effects:354 Initial tests with m1.small server instances, all test phases (connection -> 10s -> 30s -> 60s) were launched from the same (serially executed) shell script, so any delays propagated to later phases. In later tests that used m1.large server instances each subtest was precisely timed using ''at'', so this propagation of delays was eliminated. Regardless of this the delays remained, meaning that a 10 second test could easily become a 20+ second test. The culprit was not the serial nature of timing, but the incapability of the server processes - especially iperf - to establish new connections quickly started to show with as few as 20 clients. This was clearly visible when looking at server-side iperf output: clients connected with delay of several seconds. This had two effects: 355 355 356 356 * Prolonging the subtests (e.g. 10 second test could become 20+ second test) 357 357 * Artificially increased the average client bandwidth due to the head and tail of clients that had less competition (bandwidth-vise) 358 358 359 OpenVPN connection initialization seems to gomuch faster.359 OpenVPN connection initialization seems to be much faster.