From 8fdc5abffe2eec8bf08b6e1bda536e52fca4cae8 Mon Sep 17 00:00:00 2001 From: Kadir Cetinkaya Date: Tue, 16 Apr 2019 14:32:43 +0000 Subject: [PATCH] [llvm][Support] Provide interface to set thread priorities Summary: We have a multi-platform thread priority setting function(last piece landed with D58683), I wanted to make this available to all llvm community, there seem to be other users of such functionality with portability fixmes: lib/Support/CrashRecoveryContext.cpp tools/clang/tools/libclang/CIndex.cpp Reviewers: gribozavr, ioeric Subscribers: krytarowski, jfb, kristina, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D59130 llvm-svn: 358494 --- llvm/include/llvm/Support/Threading.h | 13 +++++++++ llvm/lib/Support/Unix/Threading.inc | 39 ++++++++++++++++++++++++++ llvm/lib/Support/Windows/Threading.inc | 16 +++++++++++ 3 files changed, 68 insertions(+) diff --git a/llvm/include/llvm/Support/Threading.h b/llvm/include/llvm/Support/Threading.h index 953c60f91dd4d..46d413dc487b6 100644 --- a/llvm/include/llvm/Support/Threading.h +++ b/llvm/include/llvm/Support/Threading.h @@ -167,6 +167,19 @@ void llvm_execute_on_thread(void (*UserFn)(void *), void *UserData, /// purposes, and as with setting a thread's name no indication of whether /// the operation succeeded or failed is returned. void get_thread_name(SmallVectorImpl &Name); + + enum class ThreadPriority { + Background = 0, + Default = 1, + }; + /// 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); } #endif diff --git a/llvm/lib/Support/Unix/Threading.inc b/llvm/lib/Support/Unix/Threading.inc index 767f62640bffe..ed9a96563055d 100644 --- a/llvm/lib/Support/Unix/Threading.inc +++ b/llvm/lib/Support/Unix/Threading.inc @@ -217,3 +217,42 @@ void llvm::get_thread_name(SmallVectorImpl &Name) { #endif #endif } + +SetThreadPriorityResult llvm::set_thread_priority(ThreadPriority Priority) { +#if defined(__linux__) && defined(SCHED_IDLE) + // Some *really* old glibcs are missing SCHED_IDLE. + // http://man7.org/linux/man-pages/man3/pthread_setschedparam.3.html + // http://man7.org/linux/man-pages/man2/sched_setscheduler.2.html + sched_param priority; + // For each of the above policies, param->sched_priority must be 0. + priority.sched_priority = 0; + // SCHED_IDLE for running very low priority background jobs. + // SCHED_OTHER the standard round-robin time-sharing policy; + return !pthread_setschedparam( + pthread_self(), + Priority == ThreadPriority::Background ? SCHED_IDLE : SCHED_OTHER, + &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) + ? SetThreadPriorityResult::SUCCESS + : SetThreadPriorityResult::FAILURE; +#endif + return SetThreadPriorityResult::FAILURE; +} diff --git a/llvm/lib/Support/Windows/Threading.inc b/llvm/lib/Support/Windows/Threading.inc index c53624c0dc9d0..96649472cc90b 100644 --- a/llvm/lib/Support/Windows/Threading.inc +++ b/llvm/lib/Support/Windows/Threading.inc @@ -106,3 +106,19 @@ void llvm::get_thread_name(SmallVectorImpl &Name) { // value. Name.clear(); } + +SetThreadPriorityResult llvm::set_thread_priority(ThreadPriority Priority) { + // https://docs.microsoft.com/en-us/windows/desktop/api/processthreadsapi/nf-processthreadsapi-setthreadpriority + // Begin background processing mode. The system lowers the resource scheduling + // priorities of the thread so that it can perform background work without + // significantly affecting activity in the foreground. + // End background processing mode. The system restores the resource scheduling + // priorities of the thread as they were before the thread entered background + // processing mode. + return SetThreadPriority(GetCurrentThread(), + Priority == ThreadPriority::Background + ? THREAD_MODE_BACKGROUND_BEGIN + : THREAD_MODE_BACKGROUND_END) + ? SetThreadPriorityResult::SUCCESS + : SetThreadPriorityResult::FAILURE; +}