Bring r314809 back.
But now include a check for CPU_COUNT so we still build on 10 year old
versions of glibc.
Original message:
Use sched_getaffinity instead of std::thread::hardware_concurrency.
The issue with std::thread::hardware_concurrency is that it forwards
to libc and some implementations (like glibc) don't take thread
affinity into consideration.
With this change a llvm program that can execute in only 2 cores will
use 2 threads, even if the machine has 32 cores.
This makes benchmarking a lot easier, but should also help if someone
doesn't want to use all cores for compilation for example.
llvm-svn: 314931
diff --git a/llvm/lib/Support/Parallel.cpp b/llvm/lib/Support/Parallel.cpp
index ab2cfde..010e429 100644
--- a/llvm/lib/Support/Parallel.cpp
+++ b/llvm/lib/Support/Parallel.cpp
@@ -9,6 +9,7 @@
#include "llvm/Support/Parallel.h"
#include "llvm/Config/llvm-config.h"
+#include "llvm/Support/Threading.h"
#include <atomic>
#include <stack>
@@ -70,8 +71,7 @@
/// in filo order.
class ThreadPoolExecutor : public Executor {
public:
- explicit ThreadPoolExecutor(
- unsigned ThreadCount = std::thread::hardware_concurrency())
+ explicit ThreadPoolExecutor(unsigned ThreadCount = hardware_concurrency())
: Done(ThreadCount) {
// Spawn all but one of the threads in another thread as spawning threads
// can take a while.
diff --git a/llvm/lib/Support/ThreadPool.cpp b/llvm/lib/Support/ThreadPool.cpp
index 22b7550..f1b5bdf 100644
--- a/llvm/lib/Support/ThreadPool.cpp
+++ b/llvm/lib/Support/ThreadPool.cpp
@@ -14,14 +14,15 @@
#include "llvm/Support/ThreadPool.h"
#include "llvm/Config/llvm-config.h"
+#include "llvm/Support/Threading.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#if LLVM_ENABLE_THREADS
-// Default to std::thread::hardware_concurrency
-ThreadPool::ThreadPool() : ThreadPool(std::thread::hardware_concurrency()) {}
+// Default to hardware_concurrency
+ThreadPool::ThreadPool() : ThreadPool(hardware_concurrency()) {}
ThreadPool::ThreadPool(unsigned ThreadCount)
: ActiveThreads(0), EnableFlag(true) {
diff --git a/llvm/lib/Support/Threading.cpp b/llvm/lib/Support/Threading.cpp
index 6a10b98..473c848 100644
--- a/llvm/lib/Support/Threading.cpp
+++ b/llvm/lib/Support/Threading.cpp
@@ -47,6 +47,8 @@
unsigned llvm::heavyweight_hardware_concurrency() { return 1; }
+unsigned llvm::hardware_concurrency() { return 1; }
+
uint64_t llvm::get_threadid() { return 0; }
uint32_t llvm::get_max_thread_name_length() { return 0; }
@@ -71,6 +73,18 @@
return NumPhysical;
}
+unsigned llvm::hardware_concurrency() {
+#if defined(HAVE_SCHED_GETAFFINITY) && defined(HAVE_CPU_COUNT)
+ cpu_set_t Set;
+ if (sched_getaffinity(0, sizeof(Set), &Set))
+ return CPU_COUNT(&Set);
+#endif
+ // Guard against std::thread::hardware_concurrency() returning 0.
+ if (unsigned Val = std::thread::hardware_concurrency())
+ return Val;
+ return 1;
+}
+
// Include the platform-specific parts of this class.
#ifdef LLVM_ON_UNIX
#include "Unix/Threading.inc"