126 lines
5 KiB
C++
126 lines
5 KiB
C++
/*
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* Copyright (c) 2006 The Regents of The University of Michigan
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Authors: Kevin Lim
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*/
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#ifndef __CPU_ACTIVITY_HH__
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#define __CPU_ACTIVITY_HH__
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#include "base/timebuf.hh"
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#include "base/trace.hh"
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/**
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* ActivityRecorder helper class that informs the CPU if it can switch
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* over to being idle or not. It works by having a time buffer as
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* long as any time buffer in the CPU, and the CPU and all of its
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* stages inform the ActivityRecorder when they write to any time
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* buffer. The ActivityRecorder marks a 1 in the "0" slot of the time
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* buffer any time a stage writes to a time buffer, and it advances
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* its time buffer at the same time as all other stages. The
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* ActivityRecorder also records if a stage has activity to do next
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* cycle. The recorder keeps a count of these two. Thus any time the
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* count is non-zero, there is either communication still in flight,
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* or activity that still must be done, meaning that the CPU can not
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* idle. If count is zero, then the CPU can safely idle as it has no
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* more outstanding work to do.
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*/
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class ActivityRecorder {
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public:
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ActivityRecorder(int num_stages, int longest_latency, int count);
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/** Records that there is activity this cycle. */
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void activity();
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/** Advances the activity buffer, decrementing the activityCount
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* if active communication just left the time buffer, and
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* determining if there is no activity.
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*/
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void advance();
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/** Marks a stage as active. */
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void activateStage(const int idx);
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/** Deactivates a stage. */
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void deactivateStage(const int idx);
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/** Returns how many things are active within the recorder. */
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int getActivityCount() { return activityCount; }
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/** Sets the count to a starting value. Can be used to disable
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* the idling option.
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*/
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void setActivityCount(int count)
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{ activityCount = count; }
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/** Returns if the CPU should be active. */
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bool active() { return activityCount; }
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/** Clears the time buffer and the activity count. */
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void reset();
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/** Debug function to dump the contents of the time buffer. */
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void dump();
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/** Debug function to ensure that the activity count matches the
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* contents of the time buffer.
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*/
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void validate();
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private:
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/** Time buffer that tracks if any cycles has active communication
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* in them. It should be as long as the longest communication
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* latency in the system. Each time any time buffer is written,
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* the activity buffer should also be written to. The
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* activityBuffer is advanced along with all the other time
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* buffers, so it should have a 1 somewhere in it only if there
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* is active communication in a time buffer.
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*/
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TimeBuffer<bool> activityBuffer;
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/** Longest latency time buffer in the CPU. */
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int longestLatency;
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/** Tracks how many stages and cycles of time buffer have
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* activity. Stages increment this count when they switch to
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* active, and decrement it when they switch to
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* inactive. Whenever a cycle that previously had no information
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* is written in the time buffer, this is incremented. When a
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* cycle that had information exits the time buffer due to age,
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* this count is decremented. When the count is 0, there is no
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* activity in the CPU, and it can be descheduled.
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*/
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int activityCount;
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/** Number of stages that can be marked as active or inactive. */
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int numStages;
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/** Records which stages are active/inactive. */
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bool *stageActive;
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};
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#endif // __CPU_ACTIVITY_HH__
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