From fe3c53040ab3486aa9a0e96f581f13437addec98 Mon Sep 17 00:00:00 2001
From: Azat Khuzhin <a3at.mail@gmail.com>
Date: Thu, 2 Sep 2021 21:02:35 +0300
Subject: [PATCH] Cache thread name to avoid prctl(PR_GET_NAME) for
 query_log/text_log

---
 src/Common/setThreadName.cpp | 23 ++++++++++++++++-------
 src/Common/setThreadName.h   |  2 +-
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/src/Common/setThreadName.cpp b/src/Common/setThreadName.cpp
index 9e45c62a9c9..958404b9ad1 100644
--- a/src/Common/setThreadName.cpp
+++ b/src/Common/setThreadName.cpp
@@ -22,6 +22,10 @@ namespace ErrorCodes
 }
 
 
+/// Cache thread_name to avoid prctl(PR_GET_NAME) for query_log/text_log
+static thread_local std::string thread_name;
+
+
 void setThreadName(const char * name)
 {
 #ifndef NDEBUG
@@ -40,24 +44,29 @@ void setThreadName(const char * name)
     if (0 != prctl(PR_SET_NAME, name, 0, 0, 0))
 #endif
         DB::throwFromErrno("Cannot set thread name with prctl(PR_SET_NAME, ...)", DB::ErrorCodes::PTHREAD_ERROR);
+
+    thread_name = name;
 }
 
-std::string getThreadName()
+const std::string & getThreadName()
 {
-    std::string name(16, '\0');
+    if (!thread_name.empty())
+        return thread_name;
+
+    thread_name.resize(16);
 
 #if defined(__APPLE__) || defined(OS_SUNOS)
-    if (pthread_getname_np(pthread_self(), name.data(), name.size()))
+    if (pthread_getname_np(pthread_self(), thread_name.data(), thread_name.size()))
         throw DB::Exception("Cannot get thread name with pthread_getname_np()", DB::ErrorCodes::PTHREAD_ERROR);
 #elif defined(__FreeBSD__)
 // TODO: make test. freebsd will have this function soon https://freshbsd.org/commit/freebsd/r337983
-//    if (pthread_get_name_np(pthread_self(), name.data(), name.size()))
+//    if (pthread_get_name_np(pthread_self(), thread_name.data(), thread_name.size()))
 //        throw DB::Exception("Cannot get thread name with pthread_get_name_np()", DB::ErrorCodes::PTHREAD_ERROR);
 #else
-    if (0 != prctl(PR_GET_NAME, name.data(), 0, 0, 0))
+    if (0 != prctl(PR_GET_NAME, thread_name.data(), 0, 0, 0))
         DB::throwFromErrno("Cannot get thread name with prctl(PR_GET_NAME)", DB::ErrorCodes::PTHREAD_ERROR);
 #endif
 
-    name.resize(std::strlen(name.data()));
-    return name;
+    thread_name.resize(std::strlen(thread_name.data()));
+    return thread_name;
 }
diff --git a/src/Common/setThreadName.h b/src/Common/setThreadName.h
index cdcb6b46914..ea988885db2 100644
--- a/src/Common/setThreadName.h
+++ b/src/Common/setThreadName.h
@@ -7,4 +7,4 @@
   */
 void setThreadName(const char * name);
 
-std::string getThreadName();
+const std::string & getThreadName();