benchmark: cut down http benchmark run time
This split the http/simple.js benchmark so the header settings can be benchmarked differently to reduce the time spent on this benchmark. IIUC other parameters do not have an impact on the results, see the OP of https://github.com/nodejs/node/pull/10558
Also cut the default duration to 5 seconds, on the benchmark CI we have about 20k req/sec for most types of scenarios so the results from 100k reqs should be representative enough.
cc @mscdex
Refs: https://github.com/nodejs/node/pull/18003#issuecomment-355923135
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
commit message follows commit guidelines
Affected core subsystem(s)
benchmark