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We would like to be able to see if a given hang in BHR occurred under high CPU load, as this is an indication that the hang is of less use to us, since it's likely that the external CPU use is more responsible for it. The way this works is fairly simple. We get the system CPU usage on a scale from 0 to 1, and we get the current process's CPU usage, also on a scale from 0 to 1, and we subtract the latter from the former. We then compare this value to a threshold, which is 1 - (1 / p), where p is the number of (virtual) cores on the machine. This threshold might need to be tuned, so that we require an entire physical core in order to not annotate the hang, but for now it seemed the most reasonable line in the sand. I should note that this considers CPU usage in child or parent processes as external. While we are responsible for that CPU usage, it still indicates that the stack we receive from BHR is of little value to us, since the source of the actual hang is external to that stack. MozReview-Commit-ID: JkG53zq1MdY --HG-- extra : rebase_source : 16553a9b5eac0a73cd1619c6ee01fa177ca60e58
83 lines
2.4 KiB
C++
83 lines
2.4 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_CPUUsageWatcher_h
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#define mozilla_CPUUsageWatcher_h
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#include <stdint.h>
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#include "mozilla/HangAnnotations.h"
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namespace mozilla {
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enum CPUUsageWatcherError : uint8_t
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{
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ClockGetTimeError,
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GetNumberOfProcessorsError,
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GetProcessTimesError,
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GetSystemTimesError,
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HostStatisticsError,
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ProcStatError,
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};
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class CPUUsageHangAnnotator
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: public HangMonitor::Annotator
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{
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public:
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};
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class CPUUsageWatcher
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: public HangMonitor::Annotator
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{
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public:
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CPUUsageWatcher()
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: mInitialized(false)
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, mExternalUsageThreshold(0)
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, mExternalUsageRatio(0)
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, mProcessUsageTime(0)
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, mProcessUpdateTime(0)
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, mGlobalUsageTime(0)
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, mGlobalUpdateTime(0)
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{}
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Result<Ok, CPUUsageWatcherError> Init();
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void Uninit();
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// Updates necessary values to allow AnnotateHang to function. This must be
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// called on some semi-regular basis, as it will calculate the mean CPU
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// usage values between now and the last time it was called.
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Result<Ok, CPUUsageWatcherError> CollectCPUUsage();
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void AnnotateHang(HangMonitor::HangAnnotations& aAnnotations) final;
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private:
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bool mInitialized;
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// The threshold above which we will mark a hang as occurring under high
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// external CPU usage conditions
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float mExternalUsageThreshold;
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// The CPU usage (0-1) external to our process, averaged between the two
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// most recent monitor thread runs
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float mExternalUsageRatio;
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// The total cumulative CPU usage time by our process as of the last
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// CollectCPUUsage or Startup
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uint64_t mProcessUsageTime;
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// A time value in the same units as mProcessUsageTime used to
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// determine the ratio of CPU usage time to idle time
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uint64_t mProcessUpdateTime;
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// The total cumulative CPU usage time by all processes as of the last
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// CollectCPUUsage or Startup
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uint64_t mGlobalUsageTime;
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// A time value in the same units as mGlobalUsageTime used to
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// determine the ratio of CPU usage time to idle time
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uint64_t mGlobalUpdateTime;
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// The number of virtual cores on our machine
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uint64_t mNumCPUs;
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};
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} // namespace mozilla
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#endif // mozilla_CPUUsageWatcher_h
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