hphp/runtime/vm/jit/incref-profile.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_JIT_INCREF_PROFILE_H_
  18 #define incl_HPHP_JIT_INCREF_PROFILE_H_
  19
  20 #include <folly/Format.h>
  21 #include <folly/Optional.h>
  22
  23 #include "hphp/runtime/vm/jit/target-profile.h"
  24
  25 namespace HPHP { namespace jit {
  26
  27 ///////////////////////////////////////////////////////////////////////////////
  28
  29 /*
  30  * Profile the frequency of the 3 possible different behaviors for an IncRef
  31  * instruction.  Each execution must fall into exactly one of these categories:
  32  *
  33  *  1) Uncounted:
  34  *     the type was uncounted
  35  *  2) Persistent:
  36  *     the type was refcounted and the value was persistent (so no inc happened)
  37  *  3) Incremented:
  38  *     the count for the value was incremented.
  39  *
  40  */
  41 struct IncRefProfile {
  42   uint16_t uncounted() const {
  43     return total - refcounted;
  44   }
  45
  46   uint16_t persistent() const {
  47     return refcounted - incremented;
  48   }
  49
  50   float percent(uint16_t value) const {
  51     return total ? 100.0 * value / total : 0.0;
  52   }
  53
  54   std::string toString() const {
  55     return folly::sformat(
  56       "total: {:4}\n uncounted: {:4} ({:.1f}%),\n persistent: {:4} ({:.1f}%),\n"
  57       " incremented: {:4} ({:.1f}%)",
  58       total,
  59       uncounted(),  percent(uncounted()),
  60       persistent(), percent(persistent()),
  61       incremented,  percent(incremented)
  62     );
  63   }
  64
  65   // overflow handling isn't statistically correct; but its better
  66   // than overflowing, and we're expecting threads to all have similar
  67   // distributions.
  68   static void reduce(IncRefProfile& a, const IncRefProfile& b) {
  69     auto const total = static_cast<uint32_t>(a.total + b.total);
  70     if (total > std::numeric_limits<uint16_t>::max()) {
  71       auto scale = [&] (uint16_t& x, uint64_t y) {
  72         x = (x + y) * std::numeric_limits<uint16_t>::max() / total;
  73       };
  74       a.total = std::numeric_limits<uint16_t>::max();
  75       scale(a.refcounted, b.refcounted);
  76       scale(a.incremented, b.incremented);
  77     } else {
  78       a.total       += b.total;
  79       a.refcounted  += b.refcounted;
  80       a.incremented += b.incremented;
  81     }
  82   }
  83
  84   /*
  85    * The total number of times this IncRef was executed.
  86    */
  87   uint16_t total;
  88   /*
  89    * The number of times this IncRef made it past the refcounted check.
  90    */
  91   uint16_t refcounted;
  92   /*
  93    * The number of times this IncRef actually incremented the refcount.
  94    */
  95   uint16_t incremented;
  96 };
  97
  98 ///////////////////////////////////////////////////////////////////////////////
  99
 100 } }
 101
 102 #endif