stefanhaller updated this revision to Diff 427577.
stefanhaller added a comment.
- Added a comment to setThreadBackgroundPriority
- Improved comments for ThreadPriority enum
- Add FIXME comments for Windows and Linux
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D124715/new/
https://reviews.llvm.org/D124715
Files:
clang-tools-extra/clangd/index/Background.h
clang/tools/libclang/CIndex.cpp
llvm/include/llvm/Support/Threading.h
llvm/lib/Support/Unix/Threading.inc
llvm/lib/Support/Windows/Threading.inc
Index: llvm/lib/Support/Windows/Threading.inc
===================================================================
--- llvm/lib/Support/Windows/Threading.inc
+++ llvm/lib/Support/Windows/Threading.inc
@@ -120,8 +120,10 @@
// End background processing mode. The system restores the resource scheduling
// priorities of the thread as they were before the thread entered background
// processing mode.
+ //
+ // FIXME: consider THREAD_PRIORITY_BELOW_NORMAL for Low
return SetThreadPriority(GetCurrentThread(),
- Priority == ThreadPriority::Background
+ Priority != ThreadPriority::Default
? THREAD_MODE_BACKGROUND_BEGIN
: THREAD_MODE_BACKGROUND_END)
? SetThreadPriorityResult::SUCCESS
Index: llvm/lib/Support/Unix/Threading.inc
===================================================================
--- llvm/lib/Support/Unix/Threading.inc
+++ llvm/lib/Support/Unix/Threading.inc
@@ -18,6 +18,7 @@
#if defined(__APPLE__)
#include <mach/mach_init.h>
#include <mach/mach_port.h>
+#include <pthread/qos.h>
#endif
#include <pthread.h>
@@ -258,27 +259,29 @@
// SCHED_OTHER the standard round-robin time-sharing policy;
return !pthread_setschedparam(
pthread_self(),
- Priority == ThreadPriority::Background ? SCHED_IDLE : SCHED_OTHER,
+ // FIXME: consider SCHED_BATCH for Low
+ Priority == ThreadPriority::Default ? SCHED_OTHER : SCHED_IDLE,
&priority)
? SetThreadPriorityResult::SUCCESS
: SetThreadPriorityResult::FAILURE;
#elif defined(__APPLE__)
- // https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/getpriority.2.html
- // When setting a thread into background state the scheduling priority is set
- // to lowest value, disk and network IO are throttled. Network IO will be
- // throttled for any sockets the thread opens after going into background
- // state. Any previously opened sockets are not affected.
-
- // https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man3/getiopolicy_np.3.html
- // I/Os with THROTTLE policy are called THROTTLE I/Os. If a THROTTLE I/O
- // request occurs within a small time window (usually a fraction of a second)
- // of another NORMAL I/O request, the thread that issues the THROTTLE I/O is
- // forced to sleep for a certain interval. This slows down the thread that
- // issues the THROTTLE I/O so that NORMAL I/Os can utilize most of the disk
- // I/O bandwidth.
- return !setpriority(PRIO_DARWIN_THREAD, 0,
- Priority == ThreadPriority::Background ? PRIO_DARWIN_BG
- : 0)
+ // https://developer.apple.com/documentation/apple-silicon/tuning-your-code-s-performance-for-apple-silicon
+ //
+ // Background - Applies to work that isnât visible to the user and may take significant
+ // time to complete. Examples include indexing, backing up, or synchronizing data. This
+ // class emphasizes energy efficiency.
+ //
+ // Utility - Applies to work that takes anywhere from a few seconds to a few minutes to
+ // complete. Examples include downloading a document or importing data. This class
+ // offers a balance between responsiveness, performance, and energy efficiency.
+ const auto qosClass = [&](){
+ switch (Priority) {
+ case ThreadPriority::Background: return QOS_CLASS_BACKGROUND;
+ case ThreadPriority::Low: return QOS_CLASS_UTILITY;
+ case ThreadPriority::Default: return QOS_CLASS_DEFAULT;
+ }
+ }();
+ return !pthread_set_qos_class_self_np(qosClass, 0)
? SetThreadPriorityResult::SUCCESS
: SetThreadPriorityResult::FAILURE;
#endif
Index: llvm/include/llvm/Support/Threading.h
===================================================================
--- llvm/include/llvm/Support/Threading.h
+++ llvm/include/llvm/Support/Threading.h
@@ -233,15 +233,20 @@
unsigned get_cpus();
enum class ThreadPriority {
+ /// Lower the current thread's priority as much as possible. Can be used
+ /// for long-running tasks that are not time critical; more energy-
+ /// efficient than Low.
Background = 0,
- Default = 1,
+
+ /// Lower the current thread's priority such that it does not affect
+ /// foreground tasks significantly. This is a good default for long-
+ /// running, latency-insensitive tasks to make sure cpu is not hogged
+ /// by this task.
+ Low = 1,
+
+ /// Restore the current thread's priority to default scheduling priority.
+ Default = 2,
};
- /// If priority is Background tries to lower current threads priority such
- /// that it does not affect foreground tasks significantly. Can be used for
- /// long-running, latency-insensitive tasks to make sure cpu is not hogged by
- /// this task.
- /// If the priority is default tries to restore current threads priority to
- /// default scheduling priority.
enum class SetThreadPriorityResult { FAILURE, SUCCESS };
SetThreadPriorityResult set_thread_priority(ThreadPriority Priority);
}
Index: clang/tools/libclang/CIndex.cpp
===================================================================
--- clang/tools/libclang/CIndex.cpp
+++ clang/tools/libclang/CIndex.cpp
@@ -9025,7 +9025,9 @@
return;
#if LLVM_ENABLE_THREADS
- llvm::set_thread_priority(llvm::ThreadPriority::Background);
+ // The function name setThreadBackgroundPriority is for historical reasons;
+ // Low is more appropriate.
+ llvm::set_thread_priority(llvm::ThreadPriority::Low);
#endif
}
Index: clang-tools-extra/clangd/index/Background.h
===================================================================
--- clang-tools-extra/clangd/index/Background.h
+++ clang-tools-extra/clangd/index/Background.h
@@ -72,7 +72,7 @@
explicit Task(std::function<void()> Run) : Run(std::move(Run)) {}
std::function<void()> Run;
- llvm::ThreadPriority ThreadPri = llvm::ThreadPriority::Background;
+ llvm::ThreadPriority ThreadPri = llvm::ThreadPriority::Low;
unsigned QueuePri = 0; // Higher-priority tasks will run first.
std::string Tag; // Allows priority to be boosted later.
uint64_t Key = 0; // If the key matches a previous task, drop this one.
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