gecko/tools/profiler/sps_sampler.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is
 * Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2011
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Benoit Girard <bgirard@mozilla.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include <stdlib.h>
#include <signal.h>
#include "thread_helper.h"
#include "nscore.h"
#include "jsapi.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/Util.h"

using mozilla::TimeStamp;
using mozilla::TimeDuration;

extern mozilla::tls::key pkey_stack;
extern mozilla::tls::key pkey_ticker;
extern bool stack_key_initialized;

#ifndef SAMPLE_FUNCTION_NAME
# ifdef __GNUC__
#  define SAMPLE_FUNCTION_NAME __FUNCTION__
# elif defined(_MSC_VER)
#  define SAMPLE_FUNCTION_NAME __FUNCTION__
# else
#  define SAMPLE_FUNCTION_NAME __func__  // defined in C99, supported in various C++ compilers. Just raw function name.
# endif
#endif

#define SAMPLER_INIT() mozilla_sampler_init()
#define SAMPLER_DEINIT() mozilla_sampler_deinit()
#define SAMPLER_START(entries, interval, features, featureCount) mozilla_sampler_start(entries, interval, features, featureCount)
#define SAMPLER_STOP() mozilla_sampler_stop()
#define SAMPLER_IS_ACTIVE() mozilla_sampler_is_active()
#define SAMPLER_RESPONSIVENESS(time) mozilla_sampler_responsiveness(time)
#define SAMPLER_GET_RESPONSIVENESS() mozilla_sampler_get_responsiveness()
#define SAMPLER_SAVE() mozilla_sampler_save()
#define SAMPLER_GET_PROFILE() mozilla_sampler_get_profile()
#define SAMPLER_GET_PROFILE_DATA(ctx) mozilla_sampler_get_profile_data(ctx)
#define SAMPLER_GET_FEATURES() mozilla_sampler_get_features()
// we want the class and function name but can't easily get that using preprocessor macros
// __func__ doesn't have the class name and __PRETTY_FUNCTION__ has the parameters
#define SAMPLE_LABEL(name_space, info) mozilla::SamplerStackFrameRAII only_one_sampleraii_per_scope(name_space "::" info)
#define SAMPLE_MARKER(info) mozilla_sampler_add_marker(info)

/* we duplicate this code here to avoid header dependencies
 * which make it more difficult to include in other places */
#if defined(_M_X64) || defined(__x86_64__)
#define V8_HOST_ARCH_X64 1
#elif defined(_M_IX86) || defined(__i386__) || defined(__i386)
#define V8_HOST_ARCH_IA32 1
#elif defined(__ARMEL__)
#define V8_HOST_ARCH_ARM 1
#else
#warning Please add support for your architecture in chromium_types.h
#endif

#define PROFILE_DEFAULT_ENTRY 100000
#ifdef ANDROID
// We use a lower frequency on Android, in order to make things work
// more smoothly on phones.  This value can be adjusted later with
// some libunwind optimizations.
// In one sample measurement on Galaxy Nexus, out of about 700 backtraces,
// 60 of them took more than 25ms, and the average and standard deviation
// were 6.17ms and 9.71ms respectively.
#define PROFILE_DEFAULT_INTERVAL 25
#else
#define PROFILE_DEFAULT_INTERVAL 10
#endif
#define PROFILE_DEFAULT_FEATURES NULL
#define PROFILE_DEFAULT_FEATURE_COUNT 0

// STORE_SEQUENCER: Because signals can interrupt our profile modification
//                  we need to make stores are not re-ordered by the compiler
//                  or hardware to make sure the profile is consistent at
//                  every point the signal can fire.
#ifdef V8_HOST_ARCH_ARM
// TODO Is there something cheaper that will prevent
//      memory stores from being reordered

typedef void (*LinuxKernelMemoryBarrierFunc)(void);
LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier __attribute__((weak)) =
    (LinuxKernelMemoryBarrierFunc) 0xffff0fa0;

# define STORE_SEQUENCER() pLinuxKernelMemoryBarrier()
#elif defined(V8_HOST_ARCH_IA32) || defined(V8_HOST_ARCH_X64)
# if defined(_MSC_VER)
    // MSVC2005 has a name collision bug caused when both <intrin.h> and <winnt.h> are included together.
#ifdef _WINNT_
#  define _interlockedbittestandreset _interlockedbittestandreset_NAME_CHANGED_TO_AVOID_MSVS2005_ERROR
#  define _interlockedbittestandset _interlockedbittestandset_NAME_CHANGED_TO_AVOID_MSVS2005_ERROR
#  include <intrin.h>
#else
#  include <intrin.h>
#  define _interlockedbittestandreset _interlockedbittestandreset_NAME_CHANGED_TO_AVOID_MSVS2005_ERROR
#  define _interlockedbittestandset _interlockedbittestandset_NAME_CHANGED_TO_AVOID_MSVS2005_ERROR
#endif
   // Even though MSVC2005 has the intrinsic _ReadWriteBarrier, it fails to link to it when it's
   // not explicitly declared.
#  pragma intrinsic(_ReadWriteBarrier)
#  define STORE_SEQUENCER() _ReadWriteBarrier();
# elif defined(__INTEL_COMPILER)
#  define STORE_SEQUENCER() __memory_barrier();
# elif __GNUC__
#  define STORE_SEQUENCER() asm volatile("" ::: "memory");
# else
#  error "Memory clobber not supported for your compiler."
# endif
#else
# error "Memory clobber not supported for your platform."
#endif

// Returns a handdle to pass on exit. This can check that we are popping the
// correct callstack.
inline void* mozilla_sampler_call_enter(const char *aInfo);
inline void  mozilla_sampler_call_exit(void* handle);
inline void  mozilla_sampler_add_marker(const char *aInfo);

void mozilla_sampler_start(int aEntries, int aInterval, const char** aFeatures, uint32_t aFeatureCount);
void mozilla_sampler_stop();
bool mozilla_sampler_is_active();
void mozilla_sampler_responsiveness(TimeStamp time);
const double* mozilla_sampler_get_responsiveness();
void mozilla_sampler_save();
char* mozilla_sampler_get_profile();
JSObject *mozilla_sampler_get_profile_data(JSContext *aCx);
const char** mozilla_sampler_get_features();
void mozilla_sampler_init();

namespace mozilla {

class NS_STACK_CLASS SamplerStackFrameRAII {
public:
  // we only copy the strings at save time, so to take multiple parameters we'd need to copy them then.
  SamplerStackFrameRAII(const char *aInfo) {
    mHandle = mozilla_sampler_call_enter(aInfo);
  }
  ~SamplerStackFrameRAII() {
    mozilla_sampler_call_exit(mHandle);
  }
private:
  void* mHandle;
};

} //mozilla

// the SamplerStack members are read by signal
// handlers, so the mutation of them needs to be signal-safe.
struct ProfileStack
{
public:
  ProfileStack()
    : mStackPointer(0)
    , mMarkerPointer(0)
    , mDroppedStackEntries(0)
    , mQueueClearMarker(false)
  { }

  void addMarker(const char *aMarker)
  {
    if (mQueueClearMarker) {
      clearMarkers();
    }
    if (!aMarker) {
      return; //discard
    }
    if (size_t(mMarkerPointer) == mozilla::ArrayLength(mMarkers)) {
      return; //array full, silently drop
    }
    mMarkers[mMarkerPointer] = aMarker;
    STORE_SEQUENCER();
    mMarkerPointer++;
  }

  // called within signal. Function must be reentrant
  const char* getMarker(int aMarkerId)
  {
    if (mQueueClearMarker) {
      clearMarkers();
    }
    if (aMarkerId >= mMarkerPointer) {
      return NULL;
    }
    return mMarkers[aMarkerId];
  }

  // called within signal. Function must be reentrant
  void clearMarkers()
  {
    mMarkerPointer = 0;
    mQueueClearMarker = false;
  }

  void push(const char *aName)
  {
    if (size_t(mStackPointer) >= mozilla::ArrayLength(mStack)) {
      mDroppedStackEntries++;
      return;
    }

    // Make sure we increment the pointer after the name has
    // been written such that mStack is always consistent.
    mStack[mStackPointer] = aName;
    // Prevent the optimizer from re-ordering these instructions
    STORE_SEQUENCER();
    mStackPointer++;
  }
  void pop()
  {
    if (mDroppedStackEntries > 0) {
      mDroppedStackEntries--;
    } else {
      mStackPointer--;
    }
  }
  bool isEmpty()
  {
    return mStackPointer == 0;
  }

  // Keep a list of active checkpoints
  char const * volatile mStack[1024];
  // Keep a list of active markers to be applied to the next sample taken
  char const * volatile mMarkers[1024];
  volatile mozilla::sig_safe_t mStackPointer;
  volatile mozilla::sig_safe_t mMarkerPointer;
  volatile mozilla::sig_safe_t mDroppedStackEntries;
  // We don't want to modify _markers from within the signal so we allow
  // it to queue a clear operation.
  volatile mozilla::sig_safe_t mQueueClearMarker;
};

inline void* mozilla_sampler_call_enter(const char *aInfo)
{
  // check if we've been initialized to avoid calling pthread_getspecific
  // with a null pkey_stack which will return undefined results.
  if (!stack_key_initialized)
    return NULL;

  ProfileStack *stack = mozilla::tls::get<ProfileStack>(pkey_stack);
  // we can't infer whether 'stack' has been initialized
  // based on the value of stack_key_intiailized because
  // 'stack' is only intialized when a thread is being
  // profiled.
  if (!stack) {
    return stack;
  }
  stack->push(aInfo);

  // The handle is meant to support future changes
  // but for now it is simply use to save a call to
  // pthread_getspecific on exit. It also supports the
  // case where the sampler is initialized between
  // enter and exit.
  return stack;
}

inline void mozilla_sampler_call_exit(void *aHandle)
{
  if (!aHandle)
    return;

  ProfileStack *stack = (ProfileStack*)aHandle;
  stack->pop();
}

inline void mozilla_sampler_add_marker(const char *aMarker)
{
  ProfileStack *stack = mozilla::tls::get<ProfileStack>(pkey_stack);
  if (!stack) {
    return;
  }
  stack->addMarker(aMarker);
}