[swift-dev] [Swift CI] Build Still Failing: 0. OSS - Swift Incremental RA - Ubuntu 16.10 (master) #3698

[Michael Ilseman]

Ok. If this occurs again, please update the threshold. 

> On May 17, 2017, at 12:03 PM, David P Grove <groved at us.ibm.com> wrote:
> 
> swift-dev-bounces at swift.org wrote on 05/17/2017 02:04:23 PM:
> > 
> > Failure in dispatch-starfish. This test looks timing-sensitive. 
> > Boris, is this unlikely to be related to your changes? Does anyone 
> > familiar with dispatch have suggestions, such as increasing the 
> > latency threshold?
> > 
> > [BEGIN] Latency
> > Actual: 1553
> > Expected: <1000
> > [FAIL] Latency (dispatch_starfish.c:82)
> > dispatch_starfish.c:82
> > lap: 9
> > count: 1000
> > delta: 6756400000 ns
> > math: 3374.825175 ns / lap
> > 
> > [BEGIN] Latency
> > Actual: 3374
> > Expected: <1000
> > [FAIL] Latency (dispatch_starfish.c:82)
> > dispatch_starfish.c:82
> > 
> 
> The test is subject to failing spuriously if the machine is badly overloaded.  One could increase the threshold by changing the #define on line 43 of dispatch_starfish.c
> 
> There's a trade-off between spurious failures due to overloads on build machines vs. missing performance regressions by making the latency thresholds much too lenient.  
> 
> We've been running with the current threshold in dispatch_starfish since we began running the dispatch tests in the CI system last summer.  So if this isn't a one-off failure caused by CI load, it might be pointing to an underlying performance regression.
> 
> --dave
> 
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