tree c974d5f231ce4e924c5b1030b86f7276f3bb5f02
parent fe15dd4cddcf4f42792be10c9b80e50445fadaf9
author Damien Neil <dneil@google.com> 1575915876 -0800
committer Damien Neil <dneil@google.com> 1575917982 +0000

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>