Commits on Mar 6, 2020

1. fuzz: H1 capture fuzz test performance improvements. …

   The main contribution in this patch is a "persistent" mode for
   h1_capture_[direct_response_]fuzz_test. Based on profiling observations, we were spending 30-40% of
   time rebuilding the Envoy server on each run. This is avoided by having fuzzer variants that makes
   the integration test proxy static.
   
   There is a downside of this approach, since different fuzz invocations may interfere with each
   other. Ideally we would snapshot/fork for each fuzz invocation, but Envoy doesn't like forking once
   events/dispatchers are up. So, for now we have two builds of the fuzzer, where we trade fuzz engine
   efficacy for fuzz target performance. Some form of VM snapshotting would be ideal.
   
   The persistent mode takes the H1 replay tests to O(10 exec/s) from O(1 exec/s). This is still not
   great. Doing some perf analysis, it seems that we're spending the bulk of time in ASAN. Running
   the fuzzers without ASAN gives O(100 exec/s), which seems reasonable for a LPM-style integration test.
   It's future work why ASAN is so expensive, ASAN advertises itself as generally a 2x slowdown. There
   is also some secondary effect from the cost of mocks used in the integration test TCP client (mock
   watermark buffer), this speaks to our general mocking performance problem in fuzzing.
   
   In addition to the above, this patch has an optimization for the direct response fuzzer (don't
   initiate upstream connections) and a --config=plain-fuzz mode for peformance work without
   confounding ASAN.
   
   Risk level: Low
   Testing: Manual bazel runs of the fuzzers, observing exec/s.
   
   Signed-off-by: Harvey Tuch <htuch@google.com>

   

   htuch committed Mar 6, 2020
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