f670112a59
This patch adds support for validation counters. Validation counters can be used to measure events that occur during snippet execution like cache misses to ensure that certain assumed invariants about the benchmark actually hold. Validation counters are setup within a perf event group, so are turned on and off at exactly the same time as the "group leader" counter that measures the desired value.
154 lines
4.4 KiB
C++
154 lines
4.4 KiB
C++
//===-- PerfHelper.h ------------------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// Helpers for measuring perf events.
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H
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#define LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/Config/config.h"
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#include "llvm/Support/Error.h"
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#include <cstdint>
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#include <functional>
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#include <memory>
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#ifdef _MSC_VER
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typedef int pid_t;
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#else
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#include <sys/types.h>
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#endif // _MSC_VER
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struct perf_event_attr;
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namespace llvm {
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namespace exegesis {
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namespace pfm {
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// Returns true on error.
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bool pfmInitialize();
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void pfmTerminate();
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// Retrieves the encoding for the event described by pfm_event_string.
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// NOTE: pfm_initialize() must be called before creating PerfEvent objects.
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class PerfEvent {
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public:
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// Dummy event that does not require access to counters (for tests).
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static const char *const DummyEventString;
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// http://perfmon2.sourceforge.net/manv4/libpfm.html
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// Events are expressed as strings. e.g. "INSTRUCTION_RETIRED"
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explicit PerfEvent(StringRef PfmEventString);
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PerfEvent(const PerfEvent &) = delete;
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PerfEvent(PerfEvent &&other);
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~PerfEvent();
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// The pfm_event_string passed at construction time.
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StringRef name() const;
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// Whether the event was successfully created.
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bool valid() const;
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// The encoded event to be passed to the Kernel.
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const perf_event_attr *attribute() const;
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// The fully qualified name for the event.
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// e.g. "snb_ep::INSTRUCTION_RETIRED:e=0:i=0:c=0:t=0:u=1:k=0:mg=0:mh=1"
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StringRef getPfmEventString() const;
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protected:
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PerfEvent() = default;
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std::string EventString;
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std::string FullQualifiedEventString;
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perf_event_attr *Attr;
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private:
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void initRealEvent(StringRef PfmEventString);
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};
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// Represents a single event that has been configured in the Linux perf
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// subsystem.
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class ConfiguredEvent {
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public:
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ConfiguredEvent(PerfEvent &&EventToConfigure);
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void initRealEvent(const pid_t ProcessID, const int GroupFD = -1);
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Expected<SmallVector<int64_t>> readOrError(StringRef FunctionBytes) const;
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int getFileDescriptor() const { return FileDescriptor; }
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bool isDummyEvent() const {
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return Event.name() == PerfEvent::DummyEventString;
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}
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ConfiguredEvent(const ConfiguredEvent &) = delete;
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ConfiguredEvent(ConfiguredEvent &&other) = default;
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~ConfiguredEvent();
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private:
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PerfEvent Event;
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int FileDescriptor = -1;
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};
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// Consists of a counter measuring a specific event and associated validation
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// counters measuring execution conditions. All counters in a group are part
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// of a single event group and are thus scheduled on and off the CPU as a single
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// unit.
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class CounterGroup {
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public:
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// event: the PerfEvent to measure.
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explicit CounterGroup(PerfEvent &&event, std::vector<PerfEvent> &&ValEvents,
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pid_t ProcessID = 0);
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CounterGroup(const CounterGroup &) = delete;
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CounterGroup(CounterGroup &&other) = default;
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virtual ~CounterGroup() = default;
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/// Starts the measurement of the event.
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virtual void start();
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/// Stops the measurement of the event.
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void stop();
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/// Returns the current value of the counter or error if it cannot be read.
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/// FunctionBytes: The benchmark function being executed.
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/// This is used to filter out the measurements to ensure they are only
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/// within the benchmarked code.
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/// If empty (or not specified), then no filtering will be done.
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/// Not all counters choose to use this.
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virtual llvm::Expected<llvm::SmallVector<int64_t, 4>>
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readOrError(StringRef FunctionBytes = StringRef()) const;
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virtual llvm::Expected<llvm::SmallVector<int64_t>>
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readValidationCountersOrError() const;
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virtual int numValues() const;
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int getFileDescriptor() const { return EventCounter.getFileDescriptor(); }
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protected:
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ConfiguredEvent EventCounter;
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bool IsDummyEvent;
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std::vector<ConfiguredEvent> ValidationEventCounters;
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private:
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void initRealEvent(pid_t ProcessID);
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};
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} // namespace pfm
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} // namespace exegesis
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} // namespace llvm
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#endif // LLVM_TOOLS_LLVM_EXEGESIS_PERFHELPER_H
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