CPULimiter: Refactor class to manage the CPU limitation.
This new class replaces the functionality embedded in UpdateAttempter
that limits the max CPU usage allowed by update_engine. This refactor
helps reusing this class outside of the brillo UpdateAttempter.
Bug: None
TEST=FEATURES=test emerge-link update_engine
Change-Id: Ib5487d314846b497a44bb78a3b94609571e0fe38
diff --git a/common/cpu_limiter.h b/common/cpu_limiter.h
new file mode 100644
index 0000000..c7add89
--- /dev/null
+++ b/common/cpu_limiter.h
@@ -0,0 +1,67 @@
+//
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef UPDATE_ENGINE_COMMON_CPU_LIMITER_H_
+#define UPDATE_ENGINE_COMMON_CPU_LIMITER_H_
+
+#include <brillo/message_loops/message_loop.h>
+
+namespace chromeos_update_engine {
+
+// Cgroups cpu shares constants. 1024 is the default shares a standard process
+// gets and 2 is the minimum value. We set High as a value that gives the
+// update-engine 2x the cpu share of a standard process.
+enum class CpuShares : int {
+ kHigh = 2048,
+ kNormal = 1024,
+ kLow = 2,
+};
+
+// Sets the current process shares to |shares|. Returns true on
+// success, false otherwise.
+bool SetCpuShares(CpuShares shares);
+
+class CPULimiter {
+ public:
+ CPULimiter() = default;
+ ~CPULimiter();
+
+ // Sets the cpu shares to low and sets up timeout events to stop the limiter.
+ void StartLimiter();
+
+ // Resets the cpu shares to normal and destroys any scheduled timeout sources.
+ void StopLimiter();
+
+ // Sets the cpu shares to |shares|. This method can be user at any time, but
+ // if the limiter is not running, the shares won't be reset to normal.
+ bool SetCpuShares(CpuShares shares);
+
+ private:
+ // The cpu shares timeout source callback sets the current cpu shares to
+ // normal.
+ void StopLimiterCallback();
+
+ // Current cpu shares.
+ CpuShares shares_ = CpuShares::kNormal;
+
+ // The cpu shares management timeout task id.
+ brillo::MessageLoop::TaskId manage_shares_id_{
+ brillo::MessageLoop::kTaskIdNull};
+};
+
+} // namespace chromeos_update_engine
+
+#endif // UPDATE_ENGINE_COMMON_CPU_LIMITER_H_