tree 1c149a6ee2503e14299f25a3e49d734a255864f7
parent 4a5b3fd3082794b57dadf9f962fffa5ecad974d5
author lmilewski <lmilewski@google.com> 1479315221 +0000
committer Lukasz Milewski <lmilewski@google.com> 1479316644 -0800

Add a benchmark demonstrating lock contention when Marshaling/Unmarshaling maps.

This benchmark is derived from a Google service which experienced poor performance when handling protos with maps.

The current implementation of map decoding uses reflection. In particular reflect.New, reflect.NewAt, and reflect.(*Value).Addr all call reflect.(*rvalue).ptrTo.

reflect.(*rvalue).ptrTo uses a cache protected by a mutex. Grabbing this lock is what causes the problem.

reflect.(*rvalue).ptrTo also implements a fast path (which avoids critical sections) for certain types known to the compiler. Hopefully we can extend the compiler to generate descriptors for more types (https://golang.org/issue/17931) so that we can hit the fast path for all types needed for proto decoding.
PiperOrigin-RevId: 139337589