src/sim/clocked_object.hh

   1 /*
   2  * Copyright (c) 2012-2013, 2015-2016 ARM Limited
   3  * Copyright (c) 2013 Cornell University
   4  * All rights reserved
   5  *
   6  * The license below extends only to copyright in the software and shall
   7  * not be construed as granting a license to any other intellectual
   8  * property including but not limited to intellectual property relating
   9  * to a hardware implementation of the functionality of the software
  10  * licensed hereunder.  You may use the software subject to the license
  11  * terms below provided that you ensure that this notice is replicated
  12  * unmodified and in its entirety in all distributions of the software,
  13  * modified or unmodified, in source code or in binary form.
  14  *
  15  * Redistribution and use in source and binary forms, with or without
  16  * modification, are permitted provided that the following conditions are
  17  * met: redistributions of source code must retain the above copyright
  18  * notice, this list of conditions and the following disclaimer;
  19  * redistributions in binary form must reproduce the above copyright
  20  * notice, this list of conditions and the following disclaimer in the
  21  * documentation and/or other materials provided with the distribution;
  22  * neither the name of the copyright holders nor the names of its
  23  * contributors may be used to endorse or promote products derived from
  24  * this software without specific prior written permission.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  27  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  28  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  29  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  30  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  31  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  32  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  33  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  34  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  35  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  36  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  37  *
  38  * Authors: Andreas Hansson
  39  *          Christopher Torng
  40  *          Akash Bagdia
  41  *          David Guillen Fandos
  42  */
  43
  44 /**
  45  * @file
  46  * ClockedObject declaration and implementation.
  47  */
  48
  49 #ifndef __SIM_CLOCKED_OBJECT_HH__
  50 #define __SIM_CLOCKED_OBJECT_HH__
  51
  52 #include "base/callback.hh"
  53 #include "base/intmath.hh"
  54 #include "enums/PwrState.hh"
  55 #include "params/ClockedObject.hh"
  56 #include "sim/core.hh"
  57 #include "sim/clock_domain.hh"
  58 #include "sim/sim_object.hh"
  59
  60 /**
  61  * Helper class for objects that need to be clocked. Clocked objects
  62  * typically inherit from this class. Objects that need SimObject
  63  * functionality as well should inherit from ClockedObject.
  64  */
  65 class Clocked
  66 {
  67
  68   private:
  69     // the tick value of the next clock edge (>= curTick()) at the
  70     // time of the last call to update()
  71     mutable Tick tick;
  72
  73     // The cycle counter value corresponding to the current value of
  74     // 'tick'
  75     mutable Cycles cycle;
  76
  77     /**
  78      *  Align cycle and tick to the next clock edge if not already done. When
  79      *  complete, tick must be at least curTick().
  80      */
  81     void
  82     update() const
  83     {
  84         // both tick and cycle are up-to-date and we are done, note
  85         // that the >= is important as it captures cases where tick
  86         // has already passed curTick()
  87         if (tick >= curTick())
  88             return;
  89
  90         // optimise for the common case and see if the tick should be
  91         // advanced by a single clock period
  92         tick += clockPeriod();
  93         ++cycle;
  94
  95         // see if we are done at this point
  96         if (tick >= curTick())
  97             return;
  98
  99         // if not, we have to recalculate the cycle and tick, we
 100         // perform the calculations in terms of relative cycles to
 101         // allow changes to the clock period in the future
 102         Cycles elapsedCycles(divCeil(curTick() - tick, clockPeriod()));
 103         cycle += elapsedCycles;
 104         tick += elapsedCycles * clockPeriod();
 105     }
 106
 107     /**
 108      * The clock domain this clocked object belongs to
 109      */
 110     ClockDomain &clockDomain;
 111
 112   protected:
 113
 114     /**
 115      * Create a clocked object and set the clock domain based on the
 116      * parameters.
 117      */
 118     Clocked(ClockDomain &clk_domain)
 119         : tick(0), cycle(0), clockDomain(clk_domain)
 120     {
 121         // Register with the clock domain, so that if the clock domain
 122         // frequency changes, we can update this object's tick.
 123         clockDomain.registerWithClockDomain(this);
 124     }
 125
 126     Clocked(Clocked &) = delete;
 127     Clocked &operator=(Clocked &) = delete;
 128
 129     /**
 130      * Virtual destructor due to inheritance.
 131      */
 132     virtual ~Clocked() { }
 133
 134     /**
 135      * Reset the object's clock using the current global tick value. Likely
 136      * to be used only when the global clock is reset. Currently, this done
 137      * only when Ruby is done warming up the memory system.
 138      */
 139     void
 140     resetClock() const
 141     {
 142         Cycles elapsedCycles(divCeil(curTick(), clockPeriod()));
 143         cycle = elapsedCycles;
 144         tick = elapsedCycles * clockPeriod();
 145     }
 146
 147     /**
 148      * A hook subclasses can implement so they can do any extra work that's
 149      * needed when the clock rate is changed.
 150      */
 151     virtual void clockPeriodUpdated() {}
 152
 153   public:
 154
 155     /**
 156      * Update the tick to the current tick.
 157      */
 158     void
 159     updateClockPeriod()
 160     {
 161         update();
 162         clockPeriodUpdated();
 163     }
 164
 165     /**
 166      * Determine the tick when a cycle begins, by default the current one, but
 167      * the argument also enables the caller to determine a future cycle. When
 168      * curTick() is on a clock edge, the number of cycles in the parameter is
 169      * added to curTick() to be returned. When curTick() is not aligned to a
 170      * clock edge, the number of cycles in the parameter is added to the next
 171      * clock edge.
 172      *
 173      * @param cycles The number of cycles into the future
 174      *
 175      * @return The start tick when the requested clock edge occurs. Precisely,
 176      * this tick can be
 177      *     curTick() + [0, clockPeriod()) + clockPeriod() * cycles
 178      */
 179     Tick
 180     clockEdge(Cycles cycles=Cycles(0)) const
 181     {
 182         // align tick to the next clock edge
 183         update();
 184
 185         // figure out when this future cycle is
 186         return tick + clockPeriod() * cycles;
 187     }
 188
 189     /**
 190      * Determine the current cycle, corresponding to a tick aligned to
 191      * a clock edge.
 192      *
 193      * @return When curTick() is on a clock edge, return the Cycle corresponding
 194      * to that clock edge. When curTick() is not on a clock edge, return the
 195      * Cycle corresponding to the next clock edge.
 196      */
 197     Cycles
 198     curCycle() const
 199     {
 200         // align cycle to the next clock edge.
 201         update();
 202
 203         return cycle;
 204     }
 205
 206     /**
 207      * Based on the clock of the object, determine the start tick of the first
 208      * cycle that is at least one cycle in the future. When curTick() is at the
 209      * current cycle edge, this returns the next clock edge. When calling this
 210      * during the middle of a cycle, this returns 2 clock edges in the future.
 211      *
 212      * @return The start tick of the first cycle that is at least one cycle in
 213      * the future. Precisely, the returned tick can be in the range
 214      *     curTick() + [clockPeriod(), 2 * clockPeriod())
 215      */
 216     Tick nextCycle() const { return clockEdge(Cycles(1)); }
 217
 218     uint64_t frequency() const { return SimClock::Frequency / clockPeriod(); }
 219
 220     Tick clockPeriod() const { return clockDomain.clockPeriod(); }
 221
 222     double voltage() const { return clockDomain.voltage(); }
 223
 224     Cycles
 225     ticksToCycles(Tick t) const
 226     {
 227         return Cycles(divCeil(t, clockPeriod()));
 228     }
 229
 230     Tick cyclesToTicks(Cycles c) const { return clockPeriod() * c; }
 231 };
 232
 233 /**
 234  * The ClockedObject class extends the SimObject with a clock and
 235  * accessor functions to relate ticks to the cycles of the object.
 236  */
 237 class ClockedObject : public SimObject, public Clocked
 238 {
 239   public:
 240     ClockedObject(const ClockedObjectParams *p);
 241
 242     /** Parameters of ClockedObject */
 243     typedef ClockedObjectParams Params;
 244     const Params *
 245     params() const
 246     {
 247         return reinterpret_cast<const Params*>(_params);
 248     }
 249
 250     void serialize(CheckpointOut &cp) const override;
 251     void unserialize(CheckpointIn &cp) override;
 252
 253     Enums::PwrState pwrState() const { return _currPwrState; }
 254
 255     std::string
 256     pwrStateName() const
 257     {
 258         return Enums::PwrStateStrings[_currPwrState];
 259     }
 260
 261     /** Returns the percentage residency for each power state */
 262     std::vector<double> pwrStateWeights() const;
 263
 264     /**
 265      * Record stats values like state residency by computing the time
 266      * difference from previous update. Also, updates the previous evaluation
 267      * tick once all stats are recorded.
 268      * Usually called on power state change and stats dump callback.
 269      */
 270     void computeStats();
 271
 272     void pwrState(Enums::PwrState);
 273
 274   protected:
 275
 276     /** To keep track of the current power state */
 277     Enums::PwrState _currPwrState;
 278
 279     Tick prvEvalTick;
 280
 281     struct ClockedObjectStats : public Stats::Group
 282     {
 283         ClockedObjectStats(ClockedObject &co);
 284
 285         void regStats() override;
 286         void preDumpStats() override;
 287
 288         ClockedObject &clockedObject;
 289         Stats::Scalar numPwrStateTransitions;
 290         Stats::Distribution pwrStateClkGateDist;
 291         Stats::Vector pwrStateResidencyTicks;
 292     } stats;
 293 };
 294
 295 #endif //__SIM_CLOCKED_OBJECT_HH__