perf(rmw_cyclonedds_cpp): Add thread-local caching to rmw_serialize and rmw_deserialize #561
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@@ -1842,67 +1842,113 @@ extern "C" rmw_ret_t rmw_get_serialized_message_size( | |
| return RMW_RET_UNSUPPORTED; | ||
| } | ||
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| extern "C" rmw_ret_t | ||
| rmw_serialize(const void *ros_message, | ||
| const rosidl_message_type_support_t *type_support, | ||
| rmw_serialized_message_t *serialized_message) { | ||
| // Cache the CDR writer per type_support pointer to avoid rebuilding | ||
| // make_message_value_type and make_cdr_writer on every call. | ||
| thread_local const rosidl_message_type_support_t *cached_serialize_ts = | ||
| nullptr; | ||
| thread_local std::unique_ptr<rmw_cyclonedds_cpp::BaseCDRWriter> cached_writer; | ||
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| try { | ||
| if (type_support != cached_serialize_ts) { | ||
| cached_writer = rmw_cyclonedds_cpp::make_cdr_writer( | ||
| rmw_cyclonedds_cpp::make_message_value_type(type_support)); | ||
| cached_serialize_ts = type_support; | ||
| } | ||
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| auto size = cached_writer->get_serialized_size(ros_message); | ||
| rmw_ret_t ret = rmw_serialized_message_resize(serialized_message, size); | ||
| if (RMW_RET_OK != ret) { | ||
| rmw_reset_error(); | ||
| RMW_SET_ERROR_MSG("rmw_serialize: failed to allocate space for message"); | ||
| return ret; | ||
| } | ||
| cached_writer->serialize(serialized_message->buffer, ros_message); | ||
| serialized_message->buffer_length = size; | ||
| return RMW_RET_OK; | ||
| } catch (std::exception &e) { | ||
| cached_serialize_ts = nullptr; // Invalidate cache on error | ||
| cached_writer.reset(); | ||
| RMW_SET_ERROR_MSG_WITH_FORMAT_STRING( | ||
| "rmw_serialize: failed to serialize: %s", e.what()); | ||
| return RMW_RET_ERROR; | ||
| } | ||
| } | ||
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| extern "C" rmw_ret_t | ||
| rmw_deserialize(const rmw_serialized_message_t *serialized_message, | ||
| const rosidl_message_type_support_t *type_support, | ||
| void *ros_message) { | ||
| // Cache the resolved typesupport and MessageTypeSupport per type_support | ||
| // pointer, mirroring the rmw_serialize thread-local writer cache. | ||
| // MessageTypeSupport's constructor runs std::regex_replace + ostringstream | ||
|
There was a problem hiding this comment. Does it worth to complicate the code with caching instead of fixing the root cause in the constructor by removing std::regex and std::ostringstream? E.g. something like this: template<typename MembersType>
MessageTypeSupport<MembersType>::MessageTypeSupport(const MembersType * members)
{
assert(members);
this->members_ = members;
std::string message_namespace(this->members_->message_namespace_);
std::string message_name(this->members_->message_name_);
if (!message_namespace.empty()) {
std::string::size_type pos = 0;
while ((pos = message_namespace.find("__", pos)) != std::string::npos) {
message_namespace.replace(pos, 2, "::");
pos += 2;
}
}
std::string name;
name.reserve(
message_namespace.size() + 2 + 5 + message_name.size() + 1); // "::" + "dds_::" + "_"
if (!message_namespace.empty()) {
name += message_namespace;
name += "::";
}
name += "dds_::";
name += message_name;
name += '_';
this->setName(name.c_str());
}
Member
Author
There was a problem hiding this comment. Perhaps. I'm mostly pushing this so that @jmachowinski can take a look at it as well. This was vibe coded in response to some micro-benchmarks that came up in Zulip, so I wouldn't read too much into the actual implementation versus the general idea behind it.
Member
Author
There was a problem hiding this comment. Also, the TLS caching looks really good in the mcirobenchmark because you are always publishing the same message repeatedly. In the case that you alternated the message types that you are publishing, you would constantly get cache misses, so optimizing the constructor additionally makes sense. There was a problem hiding this comment. Ah so you did in fact manage to genuinely benchmaxx the optimization @mjcarroll, I'm impressed 😂 |
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| // on every call, which adds ~400-500 ns of overhead per message. | ||
| thread_local const rosidl_message_type_support_t *cached_deser_ts = nullptr; | ||
| thread_local bool cached_is_c = false; | ||
| thread_local std::unique_ptr<rmw_cyclonedds_cpp::MessageTypeSupport< | ||
| rosidl_typesupport_introspection_c__MessageMembers>> | ||
| cached_msgts_c; | ||
| thread_local std::unique_ptr<rmw_cyclonedds_cpp::MessageTypeSupport< | ||
| rosidl_typesupport_introspection_cpp::MessageMembers>> | ||
| cached_msgts_cpp; | ||
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| bool ok; | ||
| try { | ||
| if (type_support != cached_deser_ts) { | ||
| const rosidl_message_type_support_t *ts = get_message_typesupport_handle( | ||
| type_support, rosidl_typesupport_introspection_c__identifier); | ||
| if (ts != nullptr) { | ||
| auto members = static_cast< | ||
| const rosidl_typesupport_introspection_c__MessageMembers *>( | ||
| ts->data); | ||
| cached_msgts_c = | ||
| std::make_unique<rmw_cyclonedds_cpp::MessageTypeSupport< | ||
| rosidl_typesupport_introspection_c__MessageMembers>>(members); | ||
| cached_msgts_cpp.reset(); | ||
| cached_deser_ts = type_support; | ||
| cached_is_c = true; | ||
| } else { | ||
| ts = get_message_typesupport_handle( | ||
| type_support, | ||
| rosidl_typesupport_introspection_cpp::typesupport_identifier); | ||
| if (ts != nullptr) { | ||
| auto members = static_cast< | ||
| const rosidl_typesupport_introspection_cpp::MessageMembers *>( | ||
| ts->data); | ||
| cached_msgts_cpp = | ||
| std::make_unique<rmw_cyclonedds_cpp::MessageTypeSupport< | ||
| rosidl_typesupport_introspection_cpp::MessageMembers>>( | ||
| members); | ||
| cached_msgts_c.reset(); | ||
| cached_deser_ts = type_support; | ||
| cached_is_c = false; | ||
| } else { | ||
| RMW_SET_ERROR_MSG("rmw_deserialize: type support trouble"); | ||
| return RMW_RET_ERROR; | ||
| } | ||
| } | ||
| } | ||
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| cycdeser sd(serialized_message->buffer, serialized_message->buffer_length); | ||
| if (cached_is_c) { | ||
| ok = cached_msgts_c->deserializeROSmessage(sd, ros_message, nullptr); | ||
| } else { | ||
| ok = cached_msgts_cpp->deserializeROSmessage(sd, ros_message, nullptr); | ||
| } | ||
| } catch (rmw_cyclonedds_cpp::Exception &e) { | ||
| RMW_SET_ERROR_MSG_WITH_FORMAT_STRING("rmw_serialize: %s", e.what()); | ||
| cached_deser_ts = nullptr; // Invalidate cache on error | ||
| cached_msgts_c.reset(); | ||
| cached_msgts_cpp.reset(); | ||
| ok = false; | ||
| } catch (std::runtime_error &e) { | ||
| RMW_SET_ERROR_MSG_WITH_FORMAT_STRING("rmw_serialize: %s", e.what()); | ||
| cached_deser_ts = nullptr; | ||
| cached_msgts_c.reset(); | ||
| cached_msgts_cpp.reset(); | ||
| ok = false; | ||
| } | ||
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There are still irrelevant formatting changes, it would be great to avoid them.