hphp/util/stacktrace-profiler.h

   1 /*
   2    +----------------------------------------------------------------------+
   3    | HipHop for PHP                                                       |
   4    +----------------------------------------------------------------------+
   5    | Copyright (c) 2010-present Facebook, Inc. (http://www.facebook.com)  |
   6    +----------------------------------------------------------------------+
   7    | This source file is subject to version 3.01 of the PHP license,      |
   8    | that is bundled with this package in the file LICENSE, and is        |
   9    | available through the world-wide-web at the following url:           |
  10    | http://www.php.net/license/3_01.txt                                  |
  11    | If you did not receive a copy of the PHP license and are unable to   |
  12    | obtain it through the world-wide-web, please send a note to          |
  13    | license@php.net so we can mail you a copy immediately.               |
  14    +----------------------------------------------------------------------+
  15 */
  16
  17 #ifndef incl_HPHP_PROBE_H
  18 #define incl_HPHP_PROBE_H
  19
  20 #include <string>
  21 #include <mutex>
  22 #include <atomic>
  23 #include "hphp/util/arena.h"
  24
  25 namespace HPHP {
  26
  27 /*
  28  * One single stack trace sample.  These can be generated, stored,
  29  * then passed to a StackTraceProfiler after the fact.
  30  */
  31 struct StackTraceSample {
  32   static const int kMaxDepth = 10;
  33   StackTraceSample();
  34   int depth;
  35   void* addrs[kMaxDepth];
  36 };
  37
  38 /*
  39  * A StackTraceProfiler incrementally constructs a prof-style caller tree from
  40  * the native backtrace each time its count() method is called, then dumps the
  41  * tree to stderr when destructed.
  42  *
  43  * Example usage to get two value profiles based on a bool:
  44  * void myTweakedFunction(bool personality=false) {
  45  *   static StackTraceProfiler prof_true("myCoolFunction-true");
  46  *   static StackTraceProfiler prof_false("myCoolFunction-false");
  47  *   (personality ? &prof_true : &prof_false)->count();
  48  * }
  49  *
  50  * Sometimes it is useful to disable inlining & tail-calls to make
  51  * stack traces easier to understand:
  52  *   -O2 -fno-inline -fno-optimize-sibling-calls
  53  */
  54 struct StackTraceProfiler {
  55 private:
  56   struct Node {
  57     explicit Node(void* addr) :
  58       addr(addr), callers(nullptr), next(nullptr), hits(0) {
  59     }
  60     void* const addr;
  61     Node* callers;
  62     Node* next;
  63     size_t hits;
  64   };
  65
  66 public:
  67   explicit StackTraceProfiler(std::string name, int skip = 1);
  68   ~StackTraceProfiler();
  69   StackTraceProfiler(const StackTraceProfiler& other) = delete;
  70   StackTraceProfiler& operator=(const StackTraceProfiler& other) = delete;
  71
  72   // count one call in this probe.
  73   void count();
  74   void count(const StackTraceSample&);
  75   size_t hits() const { return m_root.hits; }
  76
  77 private:
  78   static bool compareNodes(Node* a, Node* b);
  79   Node* findCaller(Node* n, void* addr);
  80   Node* makeCaller(Node* n, void* addr);
  81   void print(Node* n, std::string indent);
  82   int numLeaves(Node* n);
  83
  84 private:
  85   Arena m_arena;
  86   const std::string m_name;
  87   std::mutex m_mutex;
  88   std::atomic<bool> finishing;
  89   Node m_root;
  90   int m_skip;
  91 };
  92
  93 /*
  94  * BoolProfiler is used to collect profiled samples of a bool variable.
  95  */
  96 struct BoolProfiler {
  97   explicit BoolProfiler(std::string name);
  98   ~BoolProfiler();
  99   bool operator()(bool b);
 100 private:
 101   const std::string name;
 102   StackTraceProfiler p1, p0;
 103 };
 104
 105 /*
 106  * IntProfiler is used to collect profiled samples of an unsiged variable.
 107  * A histogram of samples are collected in power-of-2 buckets up to 64.
 108  */
 109 struct IntProfiler {
 110   explicit IntProfiler(std::string name);
 111   ~IntProfiler();
 112   void operator()(unsigned i);
 113 private:
 114   const std::string name;
 115   StackTraceProfiler pN, p64, p32, p16, p8, p4, p2, p1, p0;
 116 };
 117
 118 extern std::atomic<bool> enable_stacktrace_profiler;
 119
 120 }
 121
 122 #endif