Honor CPU counts from CFS. (#7654)

amalgamation/xgboost-all0.cc

@@ -79,6 +79,7 @@
 #include "../src/common/json.cc"
 #include "../src/common/io.cc"
 #include "../src/common/survival_util.cc"
+#include "../src/common/threading_utils.cc"
 #include "../src/common/version.cc"
 
 // c_api

include/xgboost/generic_parameters.h

@@ -13,20 +13,27 @@
 namespace xgboost {
 
 struct GenericParameter : public XGBoostParameter<GenericParameter> {
+ private:
+  // cached value for CFS CPU limit. (used in containerized env)
+  int32_t cfs_cpu_count_;  // NOLINT
+
+ public:
   // Constant representing the device ID of CPU.
   static int32_t constexpr kCpuId = -1;
   static int64_t constexpr kDefaultSeed = 0;
 
  public:
+  GenericParameter();
+
   // stored random seed
   int64_t seed { kDefaultSeed };
   // whether seed the PRNG each iteration
-  bool seed_per_iteration;
+  bool seed_per_iteration{false};
   // number of threads to use if OpenMP is enabled
   // if equals 0, use system default
   int nthread{0};
   // primary device, -1 means no gpu.
-  int gpu_id;
+  int gpu_id{kCpuId};
   // fail when gpu_id is invalid
   bool fail_on_invalid_gpu_id {false};
   bool validate_parameters {false};

src/common/threading_utils.cc

@@ -0,0 +1,51 @@
+/*!
+ * Copyright 2022 by XGBoost Contributors
+ */
+#include "threading_utils.h"
+#if defined(__linux__)
+#include <fcntl.h>
+#include <unistd.h>
+#endif  // defined(__linux__)
+#include "xgboost/logging.h"
+
+namespace xgboost {
+namespace common {
+/**
+ * \brief Get thread limit from CFS
+ *
+ * Modified from
+ * github.com/psiha/sweater/blob/master/include/boost/sweater/hardware_concurrency.hpp
+ *
+ * MIT License: Copyright (c) 2016 Domagoj Šarić
+ */
+int32_t GetCfsCPUCount() noexcept {
+#if defined(__linux__)
+  // https://bugs.openjdk.java.net/browse/JDK-8146115
+  // http://hg.openjdk.java.net/jdk/hs/rev/7f22774a5f42
+  // RAM limit /sys/fs/cgroup/memory.limit_in_bytes
+  // swap limt /sys/fs/cgroup/memory.memsw.limit_in_bytes
+
+  auto read_int = [](char const* const file_path) noexcept {
+    auto const fd(::open(file_path, O_RDONLY, 0));
+    if (fd == -1) {
+      return -1;
+    }
+    char value[64];
+    CHECK(::read(fd, value, sizeof(value)) < signed(sizeof(value)));
+    try {
+      return std::stoi(value);
+    } catch (std::exception const&) {
+      return -1;
+    }
+  };
+  // complete fair scheduler from Linux
+  auto const cfs_quota(read_int("/sys/fs/cgroup/cpu/cpu.cfs_quota_us"));
+  auto const cfs_period(read_int("/sys/fs/cgroup/cpu/cpu.cfs_period_us"));
+  if ((cfs_quota > 0) && (cfs_period > 0)) {
+    return std::max(cfs_quota / cfs_period, 1);
+  }
+#endif  //  defined(__linux__)
+  return -1;
+}
+}  // namespace common
+}  // namespace xgboost

src/common/threading_utils.h

@@ -1,7 +1,5 @@
 /*!
- * Copyright 2015-2019 by Contributors
+ * Copyright 2019-2022 by XGBoost Contributors
- * \file common.h
- * \brief Threading utilities
  */
 #ifndef XGBOOST_COMMON_THREADING_UTILS_H_
 #define XGBOOST_COMMON_THREADING_UTILS_H_
@@ -238,6 +236,8 @@ inline int32_t OmpGetThreadLimit() {
   return limit;
 }
 
+int32_t GetCfsCPUCount() noexcept;
+
 inline int32_t OmpGetNumThreads(int32_t n_threads) {
   if (n_threads <= 0) {
     n_threads = std::min(omp_get_num_procs(), omp_get_max_threads());

src/learner.cc

@@ -228,6 +228,8 @@ DMLC_REGISTER_PARAMETER(GenericParameter);
 int constexpr GenericParameter::kCpuId;
 int64_t constexpr GenericParameter::kDefaultSeed;
 
+GenericParameter::GenericParameter() : cfs_cpu_count_{common::GetCfsCPUCount()} {}
+
 void GenericParameter::ConfigureGpuId(bool require_gpu) {
 #if defined(XGBOOST_USE_CUDA)
   if (gpu_id == kCpuId) {  // 0. User didn't specify the `gpu_id'
@@ -262,7 +264,11 @@ void GenericParameter::ConfigureGpuId(bool require_gpu) {
 }
 
 int32_t GenericParameter::Threads() const {
-  return common::OmpGetNumThreads(nthread);
+  auto n_threads = common::OmpGetNumThreads(nthread);
+  if (cfs_cpu_count_ > 0) {
+    n_threads = std::min(n_threads, cfs_cpu_count_);
+  }
+  return n_threads;
 }
 
 using LearnerAPIThreadLocalStore =