internal/impl: improve extension fast path performance
Stash fast-path information for extensions on the ExtensionInfo. In
the usual case where an ExtensionType's underlying implementation is
an *ExtensionInfo, fetching the fast-path information becomes a type
assertion rather than a mutex-guarded map access.
Maintain a global sync.Map for the case where an ExtensionType isn't an
*ExtensionInfo.
Substantially improves performance for fast-path operations on
extensions:
Encode/MessageSet_type_id_before_message_content-12 267ns ± 1% 185ns ± 1% -30.44% (p=0.001 n=7+7)
Encode/basic_scalar_types_(*test.TestAllExtensions)-12 1.94µs ± 1% 0.40µs ± 1% -79.32% (p=0.000 n=8+7)
Change-Id: If048b521deb3665a090ea3d0a178c61691d4201e
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/210540
Reviewed-by: Joe Tsai <joetsai@google.com>
diff --git a/internal/impl/extension.go b/internal/impl/extension.go
index 541f4a7..0619d5d 100644
--- a/internal/impl/extension.go
+++ b/internal/impl/extension.go
@@ -38,6 +38,7 @@
goType reflect.Type
desc extensionTypeDescriptor
conv Converter
+ info *extensionFieldInfo // for fast-path method implementations
// ExtendedType is a typed nil-pointer to the parent message type that
// is being extended. It is possible for this to be unpopulated in v2
@@ -136,7 +137,8 @@
if xi.ExtensionType == nil {
xi.initToLegacy()
}
- xi.conv = NewConverter(xi.goType, xi.desc)
+ xi.conv = NewConverter(xi.goType, xi.desc.ExtensionDescriptor)
+ xi.info = makeExtensionFieldInfo(xi.desc.ExtensionDescriptor)
}
}