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
  39 /**
  40  * @file
  41  * ClockedObject declaration and implementation.
  42  */
  43
  44 #ifndef __SIM_CLOCKED_OBJECT_HH__
  45 #define __SIM_CLOCKED_OBJECT_HH__
  46
  47 #include "base/callback.hh"
  48 #include "base/intmath.hh"
  49 #include "enums/PwrState.hh"
  50 #include "params/ClockedObject.hh"
  51 #include "sim/core.hh"
  52 #include "sim/clock_domain.hh"
  53 #include "sim/sim_object.hh"
  54
  55 /**
  56  * Helper class for objects that need to be clocked. Clocked objects
  57  * typically inherit from this class. Objects that need SimObject
  58  * functionality as well should inherit from ClockedObject.
  59  */
  60 class Clocked
  61 {
  62
  63   private:
  64     // the tick value of the next clock edge (>= curTick()) at the
  65     // time of the last call to update()
  66     mutable Tick tick;
  67
  68     // The cycle counter value corresponding to the current value of
  69     // 'tick'
  70     mutable Cycles cycle;
  71
  72     /**
  73      *  Align cycle and tick to the next clock edge if not already done. When
  74      *  complete, tick must be at least curTick().
  75      */
  76     void
  77     update() const
  78     {
  79         // both tick and cycle are up-to-date and we are done, note
  80         // that the >= is important as it captures cases where tick
  81         // has already passed curTick()
  82         if (tick >= curTick())
  83             return;
  84
  85         // optimise for the common case and see if the tick should be
  86         // advanced by a single clock period
  87         tick += clockPeriod();
  88         ++cycle;
  89
  90         // see if we are done at this point
  91         if (tick >= curTick())
  92             return;
  93
  94         // if not, we have to recalculate the cycle and tick, we
  95         // perform the calculations in terms of relative cycles to
  96         // allow changes to the clock period in the future
  97         Cycles elapsedCycles(divCeil(curTick() - tick, clockPeriod()));
  98         cycle += elapsedCycles;
  99         tick += elapsedCycles * clockPeriod();
 100     }
 101
 102     /**
 103      * The clock domain this clocked object belongs to
 104      */
 105     ClockDomain &clockDomain;
 106
 107   protected:
 108
 109     /**
 110      * Create a clocked object and set the clock domain based on the
 111      * parameters.
 112      */
 113     Clocked(ClockDomain &clk_domain)
 114         : tick(0), cycle(0), clockDomain(clk_domain)
 115     {
 116         // Register with the clock domain, so that if the clock domain
 117         // frequency changes, we can update this object's tick.
 118         clockDomain.registerWithClockDomain(this);
 119     }
 120
 121     Clocked(Clocked &) = delete;
 122     Clocked &operator=(Clocked &) = delete;
 123
 124     /**
 125      * Virtual destructor due to inheritance.
 126      */
 127     virtual ~Clocked() { }
 128
 129     /**
 130      * Reset the object's clock using the current global tick value. Likely
 131      * to be used only when the global clock is reset. Currently, this done
 132      * only when Ruby is done warming up the memory system.
 133      */
 134     void
 135     resetClock() const
 136     {
 137         Cycles elapsedCycles(divCeil(curTick(), clockPeriod()));
 138         cycle = elapsedCycles;
 139         tick = elapsedCycles * clockPeriod();
 140     }
 141
 142     /**
 143      * A hook subclasses can implement so they can do any extra work that's
 144      * needed when the clock rate is changed.
 145      */
 146     virtual void clockPeriodUpdated() {}
 147
 148   public:
 149
 150     /**
 151      * Update the tick to the current tick.
 152      */
 153     void
 154     updateClockPeriod()
 155     {
 156         update();
 157         clockPeriodUpdated();
 158     }
 159
 160     /**
 161      * Determine the tick when a cycle begins, by default the current one, but
 162      * the argument also enables the caller to determine a future cycle. When
 163      * curTick() is on a clock edge, the number of cycles in the parameter is
 164      * added to curTick() to be returned. When curTick() is not aligned to a
 165      * clock edge, the number of cycles in the parameter is added to the next
 166      * clock edge.
 167      *
 168      * @param cycles The number of cycles into the future
 169      *
 170      * @return The start tick when the requested clock edge occurs. Precisely,
 171      * this tick can be
 172      *     curTick() + [0, clockPeriod()) + clockPeriod() * cycles
 173      */
 174     Tick
 175     clockEdge(Cycles cycles=Cycles(0)) const
 176     {
 177         // align tick to the next clock edge
 178         update();
 179
 180         // figure out when this future cycle is
 181         return tick + clockPeriod() * cycles;
 182     }
 183
 184     /**
 185      * Determine the current cycle, corresponding to a tick aligned to
 186      * a clock edge.
 187      *
 188      * @return When curTick() is on a clock edge, return the Cycle corresponding
 189      * to that clock edge. When curTick() is not on a clock edge, return the
 190      * Cycle corresponding to the next clock edge.
 191      */
 192     Cycles
 193     curCycle() const
 194     {
 195         // align cycle to the next clock edge.
 196         update();
 197
 198         return cycle;
 199     }
 200
 201     /**
 202      * Based on the clock of the object, determine the start tick of the first
 203      * cycle that is at least one cycle in the future. When curTick() is at the
 204      * current cycle edge, this returns the next clock edge. When calling this
 205      * during the middle of a cycle, this returns 2 clock edges in the future.
 206      *
 207      * @return The start tick of the first cycle that is at least one cycle in
 208      * the future. Precisely, the returned tick can be in the range
 209      *     curTick() + [clockPeriod(), 2 * clockPeriod())
 210      */
 211     Tick nextCycle() const { return clockEdge(Cycles(1)); }
 212
 213     uint64_t frequency() const { return SimClock::Frequency / clockPeriod(); }
 214
 215     Tick clockPeriod() const { return clockDomain.clockPeriod(); }
 216
 217     double voltage() const { return clockDomain.voltage(); }
 218
 219     Cycles
 220     ticksToCycles(Tick t) const
 221     {
 222         return Cycles(divCeil(t, clockPeriod()));
 223     }
 224
 225     Tick cyclesToTicks(Cycles c) const { return clockPeriod() * c; }
 226 };
 227
 228 /**
 229  * The ClockedObject class extends the SimObject with a clock and
 230  * accessor functions to relate ticks to the cycles of the object.
 231  */
 232 class ClockedObject : public SimObject, public Clocked
 233 {
 234   public:
 235     ClockedObject(const ClockedObjectParams *p);
 236
 237     /** Parameters of ClockedObject */
 238     typedef ClockedObjectParams Params;
 239     const Params *
 240     params() const
 241     {
 242         return reinterpret_cast<const Params*>(_params);
 243     }
 244
 245     void serialize(CheckpointOut &cp) const override;
 246     void unserialize(CheckpointIn &cp) override;
 247
 248     Enums::PwrState pwrState() const { return _currPwrState; }
 249
 250     std::string
 251     pwrStateName() const
 252     {
 253         return Enums::PwrStateStrings[_currPwrState];
 254     }
 255
 256     /** Returns the percentage residency for each power state */
 257     std::vector<double> pwrStateWeights() const;
 258
 259     /**
 260      * Record stats values like state residency by computing the time
 261      * difference from previous update. Also, updates the previous evaluation
 262      * tick once all stats are recorded.
 263      * Usually called on power state change and stats dump callback.
 264      */
 265     void computeStats();
 266
 267     void pwrState(Enums::PwrState);
 268
 269   protected:
 270
 271     /** To keep track of the current power state */
 272     Enums::PwrState _currPwrState;
 273
 274     Tick prvEvalTick;
 275
 276     struct ClockedObjectStats : public Stats::Group
 277     {
 278         ClockedObjectStats(ClockedObject &co);
 279
 280         void regStats() override;
 281         void preDumpStats() override;
 282
 283         ClockedObject &clockedObject;
 284         Stats::Scalar numPwrStateTransitions;
 285         Stats::Distribution pwrStateClkGateDist;
 286         Stats::Vector pwrStateResidencyTicks;
 287     } stats;
 288 };
 289
 290 #endif //__SIM_CLOCKED_OBJECT_HH__