lib/cpp/src/thrift/VirtualProfiling.cpp - thrift - Git at Google

 /*
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements. See the NOTICE file
  * distributed with this work for additional information
  * regarding copyright ownership. The ASF licenses this file
  * to you 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.
  */

 #include <thrift/Thrift.h>

 // Do nothing if virtual call profiling is not enabled
 #if T_GLOBAL_DEBUG_VIRTUAL > 1

 // TODO: This code only works with g++ (since we rely on the fact
 // that all std::type_info instances referring to a particular type
 // always return the exact same pointer value from name().)
 #ifndef __GNUG__
 #error "Thrift virtual function profiling currently only works with gcc"
 #endif // !__GNUG__

 // TODO: We also require glibc for the backtrace() and backtrace_symbols()
 // functions.
 #ifndef __GLIBC__
 #error "Thrift virtual function profiling currently requires glibc"
 #endif // !__GLIBC__

 #include <thrift/concurrency/Mutex.h>

 #include <ext/hash_map>
 #include <execinfo.h>
 #include <stdio.h>

 namespace apache {
 namespace thrift {

 using ::apache::thrift::concurrency::Mutex;
 using ::apache::thrift::concurrency::Guard;

 static const unsigned int MAX_STACK_DEPTH = 15;

 /**
  * A stack trace
  */
 class Backtrace {
 public:
   Backtrace(int skip = 0);
   Backtrace(Backtrace const& bt);

   void operator=(Backtrace const& bt) {
     numCallers_ = bt.numCallers_;
     if (numCallers_ >= 0) {
       memcpy(callers_, bt.callers_, numCallers_ * sizeof(void*));
     }
   }

   bool operator==(Backtrace const& bt) const { return (cmp(bt) == 0); }

   size_t hash() const {
     intptr_t ret = 0;
     for (int n = 0; n < numCallers_; ++n) {
       ret ^= reinterpret_cast<intptr_t>(callers_[n]);
     }
     return static_cast<size_t>(ret);
   }

   int cmp(Backtrace const& bt) const {
     int depth_diff = (numCallers_ - bt.numCallers_);
     if (depth_diff != 0) {
       return depth_diff;
     }

     for (int n = 0; n < numCallers_; ++n) {
       int diff = reinterpret_cast<intptr_t>(callers_[n])
                  - reinterpret_cast<intptr_t>(bt.callers_[n]);
       if (diff != 0) {
         return diff;
       }
     }

     return 0;
   }

   void print(FILE* f, int indent = 0, int start = 0) const {
     char** strings = backtrace_symbols(callers_, numCallers_);
     if (strings) {
       start += skip_;
       if (start < 0) {
         start = 0;
       }
       for (int n = start; n < numCallers_; ++n) {
         fprintf(f, "%*s#%-2d %s\n", indent, "", n, strings[n]);
       }
       free(strings);
     } else {
       fprintf(f, "%*s<failed to determine symbols>\n", indent, "");
     }
   }

   int getDepth() const { return numCallers_ - skip_; }

   void* getFrame(int index) const {
     int adjusted_index = index + skip_;
     if (adjusted_index < 0 || adjusted_index >= numCallers_) {
       return nullptr;
     }
     return callers_[adjusted_index];
   }

 private:
   void* callers_[MAX_STACK_DEPTH];
   int numCallers_;
   int skip_;
 };

 // Define the constructors non-inline, so they consistently add a single
 // frame to the stack trace, regardless of whether optimization is enabled
 Backtrace::Backtrace(int skip)
   : skip_(skip + 1) // ignore the constructor itself
 {
   numCallers_ = backtrace(callers_, MAX_STACK_DEPTH);
   if (skip_ > numCallers_) {
     skip_ = numCallers_;
   }
 }

 Backtrace::Backtrace(Backtrace const& bt) : numCallers_(bt.numCallers_), skip_(bt.skip_) {
   if (numCallers_ >= 0) {
     memcpy(callers_, bt.callers_, numCallers_ * sizeof(void*));
   }
 }

 /**
  * A backtrace, plus one or two type names
  */
 class Key {
 public:
   class Hash {
   public:
     size_t operator()(Key const& k) const { return k.hash(); }
   };

   Key(const Backtrace* bt, const std::type_info& type_info)
     : backtrace_(bt), typeName1_(type_info.name()), typeName2_(nullptr) {}

   Key(const Backtrace* bt, const std::type_info& type_info1, const std::type_info& type_info2)
     : backtrace_(bt), typeName1_(type_info1.name()), typeName2_(type_info2.name()) {}

   Key(const Key& k)
     : backtrace_(k.backtrace_), typeName1_(k.typeName1_), typeName2_(k.typeName2_) {}

   void operator=(const Key& k) {
     backtrace_ = k.backtrace_;
     typeName1_ = k.typeName1_;
     typeName2_ = k.typeName2_;
   }

   const Backtrace* getBacktrace() const { return backtrace_; }

   const char* getTypeName() const { return typeName1_; }

   const char* getTypeName2() const { return typeName2_; }

   void makePersistent() {
     // Copy the Backtrace object
     backtrace_ = new Backtrace(*backtrace_);

     // NOTE: We don't copy the type name.
     // The GNU libstdc++ implementation of type_info::name() returns a value
     // that will be valid for the lifetime of the program.  (Although the C++
     // standard doesn't guarantee this will be true on all implementations.)
   }

   /**
    * Clean up memory allocated by makePersistent()
    *
    * Should only be invoked if makePersistent() has previously been called.
    * The Key should no longer be used after cleanup() is called.
    */
   void cleanup() {
     delete backtrace_;
     backtrace_ = nullptr;
   }

   int cmp(const Key& k) const {
     int ret = backtrace_->cmp(*k.backtrace_);
     if (ret != 0) {
       return ret;
     }

     // NOTE: We compare just the name pointers.
     // With GNU libstdc++, every type_info object for the same type points to
     // exactly the same name string.  (Although this isn't guaranteed by the
     // C++ standard.)
     ret = k.typeName1_ - typeName1_;
     if (ret != 0) {
       return ret;
     }
     return k.typeName2_ - typeName2_;
   }

   bool operator==(const Key& k) const { return cmp(k) == 0; }

   size_t hash() const {
     // NOTE: As above, we just use the name pointer value.
     // Works with GNU libstdc++, but not guaranteed to be correct on all
     // implementations.
     return backtrace_->hash() ^ reinterpret_cast<size_t>(typeName1_)
            ^ reinterpret_cast<size_t>(typeName2_);
   }

 private:
   const Backtrace* backtrace_;
   const char* typeName1_;
   const char* typeName2_;
 };

 /**
  * A functor that determines which of two BacktraceMap entries
  * has a higher count.
  */
 class CountGreater {
 public:
   bool operator()(std::pair<Key, size_t> bt1, std::pair<Key, size_t> bt2) const {
     return bt1.second > bt2.second;
   }
 };

 typedef __gnu_cxx::hash_map<Key, size_t, Key::Hash> BacktraceMap;

 /**
  * A map describing how many times T_VIRTUAL_CALL() has been invoked.
  */
 BacktraceMap virtual_calls;
 Mutex virtual_calls_mutex;

 /**
  * A map describing how many times T_GENERIC_PROTOCOL() has been invoked.
  */
 BacktraceMap generic_calls;
 Mutex generic_calls_mutex;

 void _record_backtrace(BacktraceMap* map, const Mutex& mutex, Key* k) {
   Guard guard(mutex);

   BacktraceMap::iterator it = map->find(*k);
   if (it == map->end()) {
     k->makePersistent();
     map->insert(std::make_pair(*k, 1));
   } else {
     // increment the count
     // NOTE: we could assert if it->second is 0 afterwards, since that would
     // mean we've wrapped.
     ++(it->second);
   }
 }

 /**
  * Record an unnecessary virtual function call.
  *
  * This method is invoked by the T_VIRTUAL_CALL() macro.
  */
 void profile_virtual_call(const std::type_info& type) {
   int const skip = 1; // ignore this frame
   Backtrace bt(skip);
   Key k(&bt, type);
   _record_backtrace(&virtual_calls, virtual_calls_mutex, &k);
 }

 /**
  * Record a call to a template processor with a protocol that is not the one
  * specified in the template parameter.
  *
  * This method is invoked by the T_GENERIC_PROTOCOL() macro.
  */
 void profile_generic_protocol(const std::type_info& template_type,
                               const std::type_info& prot_type) {
   int const skip = 1; // ignore this frame
   Backtrace bt(skip);
   Key k(&bt, template_type, prot_type);
   _record_backtrace(&generic_calls, generic_calls_mutex, &k);
 }

 /**
  * Print the recorded profiling information to the specified file.
  */
 void profile_print_info(FILE* f) {
   typedef std::vector<std::pair<Key, size_t> > BacktraceVector;

   CountGreater is_greater;

   // Grab both locks for the duration of the print operation,
   // to ensure the output is a consistent snapshot of a single point in time
   Guard generic_calls_guard(generic_calls_mutex);
   Guard virtual_calls_guard(virtual_calls_mutex);

   // print the info from generic_calls, sorted by frequency
   //
   // We print the generic_calls info ahead of virtual_calls, since it is more
   // useful in some cases.  All T_GENERIC_PROTOCOL calls can be eliminated
   // from most programs.  Not all T_VIRTUAL_CALLs will be eliminated by
   // converting to templates.
   BacktraceVector gp_sorted(generic_calls.begin(), generic_calls.end());
   std::sort(gp_sorted.begin(), gp_sorted.end(), is_greater);

   for (BacktraceVector::const_iterator it = gp_sorted.begin(); it != gp_sorted.end(); ++it) {
     Key const& key = it->first;
     size_t const count = it->second;
     fprintf(f,
             "T_GENERIC_PROTOCOL: %zu calls to %s with a %s:\n",
             count,
             key.getTypeName(),
             key.getTypeName2());
     key.getBacktrace()->print(f, 2);
     fprintf(f, "\n");
   }

   // print the info from virtual_calls, sorted by frequency
   BacktraceVector vc_sorted(virtual_calls.begin(), virtual_calls.end());
   std::sort(vc_sorted.begin(), vc_sorted.end(), is_greater);

   for (BacktraceVector::const_iterator it = vc_sorted.begin(); it != vc_sorted.end(); ++it) {
     Key const& key = it->first;
     size_t const count = it->second;
     fprintf(f, "T_VIRTUAL_CALL: %zu calls on %s:\n", count, key.getTypeName());
     key.getBacktrace()->print(f, 2);
     fprintf(f, "\n");
   }
 }

 /**
  * Print the recorded profiling information to stdout.
  */
 void profile_print_info() {
   profile_print_info(stdout);
 }

 /**
  * Write a BacktraceMap as Google CPU profiler binary data.
  */
 static void profile_write_pprof_file(FILE* f, BacktraceMap const& map) {
   // Write the header
   uintptr_t header[5] = {0, 3, 0, 0, 0};
   fwrite(&header, sizeof(header), 1, f);

   // Write the profile records
   for (BacktraceMap::const_iterator it = map.begin(); it != map.end(); ++it) {
     uintptr_t count = it->second;
     fwrite(&count, sizeof(count), 1, f);

     Backtrace const* bt = it->first.getBacktrace();
     uintptr_t num_pcs = bt->getDepth();
     fwrite(&num_pcs, sizeof(num_pcs), 1, f);

     for (uintptr_t n = 0; n < num_pcs; ++n) {
       void* pc = bt->getFrame(n);
       fwrite(&pc, sizeof(pc), 1, f);
     }
   }

   // Write the trailer
   uintptr_t trailer[3] = {0, 1, 0};
   fwrite(&trailer, sizeof(trailer), 1, f);

   // Write /proc/self/maps
   // TODO(simpkins): This only works on linux
   FILE* proc_maps = fopen("/proc/self/maps", "r");
   if (proc_maps) {
     uint8_t buf[4096];
     while (true) {
       size_t bytes_read = fread(buf, 1, sizeof(buf), proc_maps);
       if (bytes_read == 0) {
         break;
       }
       fwrite(buf, 1, bytes_read, f);
     }
     fclose(proc_maps);
   }
 }

 /**
  * Write the recorded profiling information as pprof files.
  *
  * This writes the information using the Google CPU profiler binary data
  * format, so it can be analyzed with pprof.  Note that information about the
  * protocol/transport data types cannot be stored in this file format.
  *
  * See http://code.google.com/p/google-perftools/ for more details.
  *
  * @param gen_calls_f     The information about calls to
  *                        profile_generic_protocol() will be written to this
  *                        file.
  * @param virtual_calls_f The information about calls to
  *                        profile_virtual_call() will be written to this file.
  */
 void profile_write_pprof(FILE* gen_calls_f, FILE* virtual_calls_f) {
   typedef std::vector<std::pair<Key, size_t> > BacktraceVector;

   CountGreater is_greater;

   // Grab both locks for the duration of the print operation,
   // to ensure the output is a consistent snapshot of a single point in time
   Guard generic_calls_guard(generic_calls_mutex);
   Guard virtual_calls_guard(virtual_calls_mutex);

   // write the info from generic_calls
   profile_write_pprof_file(gen_calls_f, generic_calls);

   // write the info from virtual_calls
   profile_write_pprof_file(virtual_calls_f, virtual_calls);
 }
 }
 } // apache::thrift

 #endif // T_GLOBAL_PROFILE_VIRTUAL > 0
	/*
	* Licensed to the Apache Software Foundation (ASF) under one
	* or more contributor license agreements. See the NOTICE file
	* distributed with this work for additional information
	* regarding copyright ownership. The ASF licenses this file
	* to you 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.
	*/

	#include <thrift/Thrift.h>

	// Do nothing if virtual call profiling is not enabled
	#if T_GLOBAL_DEBUG_VIRTUAL > 1

	// TODO: This code only works with g++ (since we rely on the fact
	// that all std::type_info instances referring to a particular type
	// always return the exact same pointer value from name().)
	#ifndef __GNUG__
	#error "Thrift virtual function profiling currently only works with gcc"
	#endif // !__GNUG__

	// TODO: We also require glibc for the backtrace() and backtrace_symbols()
	// functions.
	#ifndef __GLIBC__
	#error "Thrift virtual function profiling currently requires glibc"
	#endif // !__GLIBC__

	#include <thrift/concurrency/Mutex.h>

	#include <ext/hash_map>
	#include <execinfo.h>
	#include <stdio.h>

	namespace apache {
	namespace thrift {

	using ::apache::thrift::concurrency::Mutex;
	using ::apache::thrift::concurrency::Guard;

	static const unsigned int MAX_STACK_DEPTH = 15;

	/**
	* A stack trace
	*/
	class Backtrace {
	public:
	Backtrace(int skip = 0);
	Backtrace(Backtrace const& bt);

	void operator=(Backtrace const& bt) {
	numCallers_ = bt.numCallers_;
	if (numCallers_ >= 0) {
	memcpy(callers_, bt.callers_, numCallers_ * sizeof(void*));
	}
	}

	bool operator==(Backtrace const& bt) const { return (cmp(bt) == 0); }

	size_t hash() const {
	intptr_t ret = 0;
	for (int n = 0; n < numCallers_; ++n) {
	ret ^= reinterpret_cast<intptr_t>(callers_[n]);
	}
	return static_cast<size_t>(ret);
	}

	int cmp(Backtrace const& bt) const {
	int depth_diff = (numCallers_ - bt.numCallers_);
	if (depth_diff != 0) {
	return depth_diff;
	}

	for (int n = 0; n < numCallers_; ++n) {
	int diff = reinterpret_cast<intptr_t>(callers_[n])
	- reinterpret_cast<intptr_t>(bt.callers_[n]);
	if (diff != 0) {
	return diff;
	}
	}

	return 0;
	}

	void print(FILE* f, int indent = 0, int start = 0) const {
	char** strings = backtrace_symbols(callers_, numCallers_);
	if (strings) {
	start += skip_;
	if (start < 0) {
	start = 0;
	}
	for (int n = start; n < numCallers_; ++n) {
	fprintf(f, "%*s#%-2d %s\n", indent, "", n, strings[n]);
	}
	free(strings);
	} else {
	fprintf(f, "%*s<failed to determine symbols>\n", indent, "");
	}
	}

	int getDepth() const { return numCallers_ - skip_; }

	void* getFrame(int index) const {
	int adjusted_index = index + skip_;
	if (adjusted_index < 0 \|\| adjusted_index >= numCallers_) {
	return nullptr;
	}
	return callers_[adjusted_index];
	}

	private:
	void* callers_[MAX_STACK_DEPTH];
	int numCallers_;
	int skip_;
	};

	// Define the constructors non-inline, so they consistently add a single
	// frame to the stack trace, regardless of whether optimization is enabled
	Backtrace::Backtrace(int skip)
	: skip_(skip + 1) // ignore the constructor itself
	{
	numCallers_ = backtrace(callers_, MAX_STACK_DEPTH);
	if (skip_ > numCallers_) {
	skip_ = numCallers_;
	}
	}

	Backtrace::Backtrace(Backtrace const& bt) : numCallers_(bt.numCallers_), skip_(bt.skip_) {
	if (numCallers_ >= 0) {
	memcpy(callers_, bt.callers_, numCallers_ * sizeof(void*));
	}
	}

	/**
	* A backtrace, plus one or two type names
	*/
	class Key {
	public:
	class Hash {
	public:
	size_t operator()(Key const& k) const { return k.hash(); }
	};

	Key(const Backtrace* bt, const std::type_info& type_info)
	: backtrace_(bt), typeName1_(type_info.name()), typeName2_(nullptr) {}

	Key(const Backtrace* bt, const std::type_info& type_info1, const std::type_info& type_info2)
	: backtrace_(bt), typeName1_(type_info1.name()), typeName2_(type_info2.name()) {}

	Key(const Key& k)
	: backtrace_(k.backtrace_), typeName1_(k.typeName1_), typeName2_(k.typeName2_) {}

	void operator=(const Key& k) {
	backtrace_ = k.backtrace_;
	typeName1_ = k.typeName1_;
	typeName2_ = k.typeName2_;
	}

	const Backtrace* getBacktrace() const { return backtrace_; }

	const char* getTypeName() const { return typeName1_; }

	const char* getTypeName2() const { return typeName2_; }

	void makePersistent() {
	// Copy the Backtrace object
	backtrace_ = new Backtrace(*backtrace_);

	// NOTE: We don't copy the type name.
	// The GNU libstdc++ implementation of type_info::name() returns a value
	// that will be valid for the lifetime of the program. (Although the C++
	// standard doesn't guarantee this will be true on all implementations.)
	}

	/**
	* Clean up memory allocated by makePersistent()
	*
	* Should only be invoked if makePersistent() has previously been called.
	* The Key should no longer be used after cleanup() is called.
	*/
	void cleanup() {
	delete backtrace_;
	backtrace_ = nullptr;
	}

	int cmp(const Key& k) const {
	int ret = backtrace_->cmp(*k.backtrace_);
	if (ret != 0) {
	return ret;
	}

	// NOTE: We compare just the name pointers.
	// With GNU libstdc++, every type_info object for the same type points to
	// exactly the same name string. (Although this isn't guaranteed by the
	// C++ standard.)
	ret = k.typeName1_ - typeName1_;
	if (ret != 0) {
	return ret;
	}
	return k.typeName2_ - typeName2_;
	}

	bool operator==(const Key& k) const { return cmp(k) == 0; }

	size_t hash() const {
	// NOTE: As above, we just use the name pointer value.
	// Works with GNU libstdc++, but not guaranteed to be correct on all
	// implementations.
	return backtrace_->hash() ^ reinterpret_cast<size_t>(typeName1_)
	^ reinterpret_cast<size_t>(typeName2_);
	}

	private:
	const Backtrace* backtrace_;
	const char* typeName1_;
	const char* typeName2_;
	};

	/**
	* A functor that determines which of two BacktraceMap entries
	* has a higher count.
	*/
	class CountGreater {
	public:
	bool operator()(std::pair<Key, size_t> bt1, std::pair<Key, size_t> bt2) const {
	return bt1.second > bt2.second;
	}
	};

	typedef __gnu_cxx::hash_map<Key, size_t, Key::Hash> BacktraceMap;

	/**
	* A map describing how many times T_VIRTUAL_CALL() has been invoked.
	*/
	BacktraceMap virtual_calls;
	Mutex virtual_calls_mutex;

	/**
	* A map describing how many times T_GENERIC_PROTOCOL() has been invoked.
	*/
	BacktraceMap generic_calls;
	Mutex generic_calls_mutex;

	void _record_backtrace(BacktraceMap* map, const Mutex& mutex, Key* k) {
	Guard guard(mutex);

	BacktraceMap::iterator it = map->find(*k);
	if (it == map->end()) {
	k->makePersistent();
	map->insert(std::make_pair(*k, 1));
	} else {
	// increment the count
	// NOTE: we could assert if it->second is 0 afterwards, since that would
	// mean we've wrapped.
	++(it->second);
	}
	}

	/**
	* Record an unnecessary virtual function call.
	*
	* This method is invoked by the T_VIRTUAL_CALL() macro.
	*/
	void profile_virtual_call(const std::type_info& type) {
	int const skip = 1; // ignore this frame
	Backtrace bt(skip);
	Key k(&bt, type);
	_record_backtrace(&virtual_calls, virtual_calls_mutex, &k);
	}

	/**
	* Record a call to a template processor with a protocol that is not the one
	* specified in the template parameter.
	*
	* This method is invoked by the T_GENERIC_PROTOCOL() macro.
	*/
	void profile_generic_protocol(const std::type_info& template_type,
	const std::type_info& prot_type) {
	int const skip = 1; // ignore this frame
	Backtrace bt(skip);
	Key k(&bt, template_type, prot_type);
	_record_backtrace(&generic_calls, generic_calls_mutex, &k);
	}

	/**
	* Print the recorded profiling information to the specified file.
	*/
	void profile_print_info(FILE* f) {
	typedef std::vector<std::pair<Key, size_t> > BacktraceVector;

	CountGreater is_greater;

	// Grab both locks for the duration of the print operation,
	// to ensure the output is a consistent snapshot of a single point in time
	Guard generic_calls_guard(generic_calls_mutex);
	Guard virtual_calls_guard(virtual_calls_mutex);

	// print the info from generic_calls, sorted by frequency
	//
	// We print the generic_calls info ahead of virtual_calls, since it is more
	// useful in some cases. All T_GENERIC_PROTOCOL calls can be eliminated
	// from most programs. Not all T_VIRTUAL_CALLs will be eliminated by
	// converting to templates.
	BacktraceVector gp_sorted(generic_calls.begin(), generic_calls.end());
	std::sort(gp_sorted.begin(), gp_sorted.end(), is_greater);

	for (BacktraceVector::const_iterator it = gp_sorted.begin(); it != gp_sorted.end(); ++it) {
	Key const& key = it->first;
	size_t const count = it->second;
	fprintf(f,
	"T_GENERIC_PROTOCOL: %zu calls to %s with a %s:\n",
	count,
	key.getTypeName(),
	key.getTypeName2());
	key.getBacktrace()->print(f, 2);
	fprintf(f, "\n");
	}

	// print the info from virtual_calls, sorted by frequency
	BacktraceVector vc_sorted(virtual_calls.begin(), virtual_calls.end());
	std::sort(vc_sorted.begin(), vc_sorted.end(), is_greater);

	for (BacktraceVector::const_iterator it = vc_sorted.begin(); it != vc_sorted.end(); ++it) {
	Key const& key = it->first;
	size_t const count = it->second;
	fprintf(f, "T_VIRTUAL_CALL: %zu calls on %s:\n", count, key.getTypeName());
	key.getBacktrace()->print(f, 2);
	fprintf(f, "\n");
	}
	}

	/**
	* Print the recorded profiling information to stdout.
	*/
	void profile_print_info() {
	profile_print_info(stdout);
	}

	/**
	* Write a BacktraceMap as Google CPU profiler binary data.
	*/
	static void profile_write_pprof_file(FILE* f, BacktraceMap const& map) {
	// Write the header
	uintptr_t header[5] = {0, 3, 0, 0, 0};
	fwrite(&header, sizeof(header), 1, f);

	// Write the profile records
	for (BacktraceMap::const_iterator it = map.begin(); it != map.end(); ++it) {
	uintptr_t count = it->second;
	fwrite(&count, sizeof(count), 1, f);

	Backtrace const* bt = it->first.getBacktrace();
	uintptr_t num_pcs = bt->getDepth();
	fwrite(&num_pcs, sizeof(num_pcs), 1, f);

	for (uintptr_t n = 0; n < num_pcs; ++n) {
	void* pc = bt->getFrame(n);
	fwrite(&pc, sizeof(pc), 1, f);
	}
	}

	// Write the trailer
	uintptr_t trailer[3] = {0, 1, 0};
	fwrite(&trailer, sizeof(trailer), 1, f);

	// Write /proc/self/maps
	// TODO(simpkins): This only works on linux
	FILE* proc_maps = fopen("/proc/self/maps", "r");
	if (proc_maps) {
	uint8_t buf[4096];
	while (true) {
	size_t bytes_read = fread(buf, 1, sizeof(buf), proc_maps);
	if (bytes_read == 0) {
	break;
	}
	fwrite(buf, 1, bytes_read, f);
	}
	fclose(proc_maps);
	}
	}

	/**
	* Write the recorded profiling information as pprof files.
	*
	* This writes the information using the Google CPU profiler binary data
	* format, so it can be analyzed with pprof. Note that information about the
	* protocol/transport data types cannot be stored in this file format.
	*
	* See http://code.google.com/p/google-perftools/ for more details.
	*
	* @param gen_calls_f The information about calls to
	* profile_generic_protocol() will be written to this
	* file.
	* @param virtual_calls_f The information about calls to
	* profile_virtual_call() will be written to this file.
	*/
	void profile_write_pprof(FILE* gen_calls_f, FILE* virtual_calls_f) {
	typedef std::vector<std::pair<Key, size_t> > BacktraceVector;

	CountGreater is_greater;

	// Grab both locks for the duration of the print operation,
	// to ensure the output is a consistent snapshot of a single point in time
	Guard generic_calls_guard(generic_calls_mutex);
	Guard virtual_calls_guard(virtual_calls_mutex);

	// write the info from generic_calls
	profile_write_pprof_file(gen_calls_f, generic_calls);

	// write the info from virtual_calls
	profile_write_pprof_file(virtual_calls_f, virtual_calls);
	}
	}
	} // apache::thrift

	#endif // T_GLOBAL_PROFILE_VIRTUAL > 0