[lldb-dev] possible test runner speedup

Pavel Labath via lldb-dev lldb-dev at lists.llvm.org
Mon Sep 28 02:12:43 PDT 2015


Interesting results. We were discussing the same thing last week. I
was somewhat skeptical to the ideal as I am afraid of increased
flakyness -- LLDB has hardcoded timeout values in a lot of places, and
with increased cpu contention, we might start to see this code failing
because the other side was slower than expected.

I have now tried running the test suite with a higher number of
threads and it seems it working quite alright, so I think we can try
that. I'll watch the buildbots for signs of increased flakyness. FWIW,
it did not speed up the tests for me at all, but I guess that's
expected, as it ran in 90 seconds even before that, and the limiting
factor there probably is the longest test.

As for the timeout, I have set the value to 4 minutes, based on the
formula: 2 * (number of seconds when I first started noticing flaky
tests in the slowest configuration). The slowest configuration here
was running the test suite on a debug build of lldb and using debug
ToT clang to compile the inferiors (believe it or not, this makes a
big difference). So there is still some leeway here, but if you're
gonna reduce the default, please make sure it is enough for the
slowest test configuration also. For faster configurations you can
always override the timeout manually.


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