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Posted to notifications@logging.apache.org by GitBox <gi...@apache.org> on 2022/11/07 03:53:57 UTC
[GitHub] [logging-log4cxx] swebb2066 opened a new pull request, #148: Reduce std::ostream logging overhead
swebb2066 opened a new pull request, #148:
URL: https://github.com/apache/logging-log4cxx/pull/148
This PR reduces the overhead of logging values through `operator<<(std::ostream&` by using a thread local std::basic_ostringstream where available.
It retains the static string logging optimization, thereby resolving the issue with the previous attempt (Thorsten Schöning 2018-08-19) to introduce this optimization.
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[GitHub] [logging-log4cxx] swebb2066 merged pull request #148: Reduce std::ostream logging overhead
Posted by GitBox <gi...@apache.org>.
swebb2066 merged PR #148:
URL: https://github.com/apache/logging-log4cxx/pull/148
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[GitHub] [logging-log4cxx] rm5248 commented on a diff in pull request #148: Reduce std::ostream logging overhead
Posted by GitBox <gi...@apache.org>.
rm5248 commented on code in PR #148:
URL: https://github.com/apache/logging-log4cxx/pull/148#discussion_r1015347242
##########
src/main/cpp/messagebuffer.cpp:
##########
@@ -149,10 +118,14 @@ CharMessageBuffer& CharMessageBuffer::operator<<(const char msg)
CharMessageBuffer::operator std::basic_ostream<char>& ()
{
- if (m_priv->stream == 0)
+ if (!m_priv->stream)
{
+#if LOG4CXX_HAS_THREAD_LOCAL
+ thread_local static std::basic_ostringstream<char> sStream;
+ m_priv->stream = &sStream;
+#else
m_priv->stream = new std::basic_ostringstream<char>();
-
+#endif
Review Comment:
At this point I'm not aware of any compiler that supports C++11 but not `thread_local`, would it make sense to simply make `m_priv->stream` a `thread_local` variable instead of holding a pointer? I could be wrong here, but it looks like if two threads are logging at the same time they could both get the same `ostringstream`, thus defeating the purpose of the `thread_local`.
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[GitHub] [logging-log4cxx] swebb2066 commented on a diff in pull request #148: Reduce std::ostream logging overhead
Posted by GitBox <gi...@apache.org>.
swebb2066 commented on code in PR #148:
URL: https://github.com/apache/logging-log4cxx/pull/148#discussion_r1015945163
##########
src/main/cpp/messagebuffer.cpp:
##########
@@ -149,10 +118,14 @@ CharMessageBuffer& CharMessageBuffer::operator<<(const char msg)
CharMessageBuffer::operator std::basic_ostream<char>& ()
{
- if (m_priv->stream == 0)
+ if (!m_priv->stream)
{
+#if LOG4CXX_HAS_THREAD_LOCAL
+ thread_local static std::basic_ostringstream<char> sStream;
+ m_priv->stream = &sStream;
+#else
m_priv->stream = new std::basic_ostringstream<char>();
-
+#endif
Review Comment:
> would it make sense to simply make `m_priv->stream` a `thread_local `variable instead of holding a pointer
The `m_priv->stream` must be zero when logging only `std::string` or `char* ` to implement the static string logging optimization.
> looks like if two threads are logging at the same time they could both get the same ostringstream
The `thread_local ` implementation should ensure the sSteam obtained by each thread will be different, and the `m_priv->stream` pointer life-time is the `MessageBuffer` lifetime. The only way two threads could share the same `ostringstream` is if the user provides a `MessageBuffer` object reference to the other thread. `MessageBuffer` is not intended to be used outside LOG4CXX_* macros.
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