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Posted to github@trafficserver.apache.org by GitBox <gi...@apache.org> on 2022/04/18 22:39:14 UTC
[GitHub] [trafficserver] cmcfarlen commented on a diff in pull request #8581: Reduce overhead incurred by enabling debug output.
cmcfarlen commented on code in PR #8581:
URL: https://github.com/apache/trafficserver/pull/8581#discussion_r852451453
##########
src/tscore/DbgCtl.cc:
##########
@@ -0,0 +1,111 @@
+/** @file
+
+ Implementation file for DbgCtl class.
+
+ @section license License
+
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements. See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership. The ASF licenses this file
+ to you under the Apache License, Version 2.0 (the
+ "License"); you may not use this file except in compliance
+ with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+#include <mutex>
+#include <atomic>
+#include <set>
+#include <cstring>
+
+#include <tscore/Diags.h>
+
+// The resistry of fast debug controllers has a ugly implementation to handle the whole-program initialization
+// order problem with C++.
Review Comment:
Can you explain how this handles the whole-program init order problem? Also, a general summary of the approach here how the debug tags are assembled into this registry and efficiently checked.
##########
include/tscore/DbgCtl.h:
##########
@@ -0,0 +1,56 @@
+/** @file
+
+ DbgCtl class header file.
+
+ @section license License
+
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements. See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership. The ASF licenses this file
+ to you under the Apache License, Version 2.0 (the
+ "License"); you may not use this file except in compliance
+ with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+#pragma once
+
+#include <ts/ts.h>
+
+// For use with TSDbg().
+//
+class DbgCtl
+{
+public:
+ // Tag is a debug tag. Debug output associated with this control will be output when debug output
+ // is enabled globally, and the tag matches the configured debug tag regular expression.
+ //
+ DbgCtl(char const *tag) : _ptr(_get_ptr(tag)) {}
Review Comment:
Could call `TSDbgCtlCreate` instead of `_get_ptr` directly to get the asserts
##########
src/tscore/DbgCtl.cc:
##########
@@ -0,0 +1,111 @@
+/** @file
+
+ Implementation file for DbgCtl class.
+
+ @section license License
+
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements. See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership. The ASF licenses this file
+ to you under the Apache License, Version 2.0 (the
+ "License"); you may not use this file except in compliance
+ with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+
+#include <mutex>
+#include <atomic>
+#include <set>
+#include <cstring>
+
+#include <tscore/Diags.h>
+
+// The resistry of fast debug controllers has a ugly implementation to handle the whole-program initialization
+// order problem with C++.
+//
+class DbgCtl::_RegistryAccessor
+{
+private:
+ struct TagCmp {
+ bool
+ operator()(TSDbgCtl const &a, TSDbgCtl const &b) const
+ {
+ return std::strcmp(a.tag, b.tag) < 0;
+ }
+ };
+
+public:
+ _RegistryAccessor() : _lg(data().mtx) {}
+
+ using Set = std::set<TSDbgCtl, TagCmp>;
+
+ struct Data {
+ std::mutex mtx;
+ Set set;
+ };
+
+ static Data &
+ data()
+ {
+ static Data d;
+ return d;
+ }
+
+private:
+ std::lock_guard<std::mutex> _lg;
+};
+
+TSDbgCtl const *
+DbgCtl::_get_ptr(char const *tag)
+{
+ ink_assert(tag != nullptr);
+
+ TSDbgCtl ctl;
+
+ ctl.tag = tag;
+
+ _RegistryAccessor ra;
+
+ auto &d{ra.data()};
+
+ if (auto it = d.set.find(ctl); it != d.set.end()) {
+ return &*it;
+ }
+
+ auto sz = std::strlen(tag);
+
+ ink_assert(sz > 0);
+
+ {
+ char *t = new char[sz + 1]; // Deleted implicitly by program termination.
Review Comment:
🤔Not sure a memcheck tool would agree.
##########
include/tscore/Diags.h:
##########
@@ -142,50 +156,93 @@ extern Diags *diags;
/// A Diag version of the above.
#define Diag(tag, ...) \
do { \
- if (unlikely(diags->on())) { \
+ if (unlikely(diags()->on())) { \
static const SourceLocation loc = MakeSourceLocation(); \
static LogMessage log_message; \
log_message.diag(tag, loc, __VA_ARGS__); \
} \
- } while (0)
-
-/// A Debug version of the above.
-#define Debug(tag, ...) \
- do { \
- if (unlikely(diags->on())) { \
- static const SourceLocation loc = MakeSourceLocation(); \
- static LogMessage log_message; \
- log_message.debug(tag, loc, __VA_ARGS__); \
- } \
- } while (0)
-
-/** Same as Debug above, but this allows a positive override of the tag
- * mechanism by a flag boolean.
- *
- * @param[in] flag True if the message should be logged regardless of tag
- * configuration, false if the logging of the message should respsect the tag
- * configuration.
- */
-#define SpecificDebug(flag, tag, ...) \
- do { \
- if (unlikely(diags->on())) { \
- static const SourceLocation loc = MakeSourceLocation(); \
- static LogMessage log_message; \
- flag ? log_message.print(tag, DL_Debug, loc, __VA_ARGS__) : log_message.debug(tag, loc, __VA_ARGS__); \
- } \
- } while (0)
-
-#define is_debug_tag_set(_t) unlikely(diags->on(_t, DiagsTagType_Debug))
-#define is_action_tag_set(_t) unlikely(diags->on(_t, DiagsTagType_Action))
+ } while (false)
+
+inline bool
+is_dbg_ctl_enabled(DbgCtl const &ctl)
+{
+ return unlikely(diags()->on()) && ctl.ptr()->on;
+}
+
+// printf-line debug output. First parameter must be DbgCtl instance. Assumes debug control is enabled, and
+// debug output globablly enabled.
+//
+#define DbgPrint(ctl__, ...) \
+ do { \
+ static const SourceLocation loc__ = MakeSourceLocation(); \
+ static LogMessage log_message__; \
+ log_message__.print(ctl__.ptr()->tag, DL_Debug, loc__, __VA_ARGS__); \
+ } while (false)
+
+// printf-like debug output. First parameter must be an instance of DbgCtl.
+//
+#define Dbg(ctl__, ...) \
+ do { \
+ if (unlikely(diags()->on()) && ctl__.ptr()->on) { \
+ DbgPrint(ctl__, __VA_ARGS__); \
+ } \
+ } while (false)
+
+// printf-like debug output. First parameter must be tag (C-string literal, or otherwise
+// a constexpr returning char const pointer to null-terminated C-string).
+//
+#define Debug(tag__, ...) \
+ do { \
+ if (unlikely(diags()->on())) { \
+ static DbgCtl ctl__(tag__); \
Review Comment:
identifiers with double underscores are reserved for the implementation.
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