From: Teresa Johnson <tejohnson@google.com>
Date: Wed, 19 Oct 2016 17:35:01 +0000 (+0000)
Subject: [ThinLTO] Default backend threads to heavyweight_hardware_concurrency
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=740d871c3ea53e7f90f0f1a848189ccdd17acb3d;p=llvm

[ThinLTO] Default backend threads to heavyweight_hardware_concurrency

Summary:
Changes default backend parallelism from thread::hardware_concurrency to
the new llvm::heavyweight_hardware_concurrency, which for X86 Linux
defaults to the number of physical cores (and will fall back to
thread::hardware_concurrency otherwise). This avoid oversubscribing
the physical cores using hyperthreading.

Reviewers: mehdi_amini, pcc

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D25775

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284618 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/LTO/LTO.cpp b/lib/LTO/LTO.cpp
index 65bcef6370d..b4efb4a4db6 100644
--- a/lib/LTO/LTO.cpp
+++ b/lib/LTO/LTO.cpp
@@ -29,6 +29,7 @@
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/ThreadPool.h"
+#include "llvm/Support/Threading.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
@@ -227,7 +228,8 @@ LTO::RegularLTOState::RegularLTOState(unsigned ParallelCodeGenParallelismLevel,
 
 LTO::ThinLTOState::ThinLTOState(ThinBackend Backend) : Backend(Backend) {
   if (!Backend)
-    this->Backend = createInProcessThinBackend(thread::hardware_concurrency());
+    this->Backend =
+        createInProcessThinBackend(llvm::heavyweight_hardware_concurrency());
 }
 
 LTO::LTO(Config Conf, ThinBackend Backend,
diff --git a/lib/LTO/ThinLTOCodeGenerator.cpp b/lib/LTO/ThinLTOCodeGenerator.cpp
index 10af9870ccb..578b3e88b01 100644
--- a/lib/LTO/ThinLTOCodeGenerator.cpp
+++ b/lib/LTO/ThinLTOCodeGenerator.cpp
@@ -43,6 +43,7 @@
 #include "llvm/Support/SHA1.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/ThreadPool.h"
+#include "llvm/Support/Threading.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/IPO/FunctionImport.h"
@@ -64,8 +65,8 @@ extern cl::opt<bool> LTODiscardValueNames;
 
 namespace {
 
-static cl::opt<int> ThreadCount("threads",
-                                cl::init(std::thread::hardware_concurrency()));
+static cl::opt<int>
+    ThreadCount("threads", cl::init(llvm::heavyweight_hardware_concurrency()));
 
 static void diagnosticHandler(const DiagnosticInfo &DI) {
   DiagnosticPrinterRawOStream DP(errs());
diff --git a/tools/gold/gold-plugin.cpp b/tools/gold/gold-plugin.cpp
index 055c462e69a..1366c0f77fd 100644
--- a/tools/gold/gold-plugin.cpp
+++ b/tools/gold/gold-plugin.cpp
@@ -118,8 +118,8 @@ namespace options {
   static unsigned OptLevel = 2;
   // Default parallelism of 0 used to indicate that user did not specify.
   // Actual parallelism default value depends on implementation.
-  // Currently only affects ThinLTO, where the default is the
-  // hardware_concurrency.
+  // Currently only affects ThinLTO, where the default is
+  // llvm::heavyweight_hardware_concurrency.
   static unsigned Parallelism = 0;
   // Default regular LTO codegen parallelism (number of partitions).
   static unsigned ParallelCodeGenParallelismLevel = 1;
diff --git a/tools/llvm-lto2/llvm-lto2.cpp b/tools/llvm-lto2/llvm-lto2.cpp
index a3cc6ef14d1..042f874596f 100644
--- a/tools/llvm-lto2/llvm-lto2.cpp
+++ b/tools/llvm-lto2/llvm-lto2.cpp
@@ -20,6 +20,7 @@
 #include "llvm/LTO/LTO.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/TargetSelect.h"
+#include "llvm/Support/Threading.h"
 
 using namespace llvm;
 using namespace lto;
@@ -52,7 +53,7 @@ static cl::opt<bool>
                                        "distributed backend case"));
 
 static cl::opt<int> Threads("-thinlto-threads",
-                            cl::init(thread::hardware_concurrency()));
+                            cl::init(llvm::heavyweight_hardware_concurrency()));
 
 static cl::list<std::string> SymbolResolutions(
     "r",