activity.hh revision 2348
1/* 2 * Copyright (c) 2006 The Regents of The University of Michigan 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions are 7 * met: redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer; 9 * redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution; 12 * neither the name of the copyright holders nor the names of its 13 * contributors may be used to endorse or promote products derived from 14 * this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29#ifndef __CPU_ACTIVITY_HH__ 30#define __CPU_ACTIVITY_HH__ 31 32#include "base/timebuf.hh" 33#include "base/trace.hh" 34 35/** 36 * ActivityRecorder helper class that informs the CPU if it can switch 37 * over to being idle or not. It works by having a time buffer as 38 * long as any time buffer in the CPU, and the CPU and all of its 39 * stages inform the ActivityRecorder when they write to any time 40 * buffer. The ActivityRecorder marks a 1 in the "0" slot of the time 41 * buffer any time a stage writes to a time buffer, and it advances 42 * its time buffer at the same time as all other stages. The 43 * ActivityRecorder also records if a stage has activity to do next 44 * cycle. The recorder keeps a count of these two. Thus any time the 45 * count is non-zero, there is either communication still in flight, 46 * or activity that still must be done, meaning that the CPU can not 47 * idle. If count is zero, then the CPU can safely idle as it has no 48 * more outstanding work to do. 49 */ 50class ActivityRecorder { 51 public: 52 ActivityRecorder(int num_stages, int longest_latency, int count); 53 54 /** Records that there is activity this cycle. */ 55 void activity(); 56 57 /** Advances the activity buffer, decrementing the activityCount 58 * if active communication just left the time buffer, and 59 * determining if there is no activity. 60 */ 61 void advance(); 62 63 /** Marks a stage as active. */ 64 void activateStage(const int idx); 65 66 /** Deactivates a stage. */ 67 void deactivateStage(const int idx); 68 69 /** Returns how many things are active within the recorder. */ 70 int getActivityCount() { return activityCount; } 71 72 /** Sets the count to a starting value. Can be used to disable 73 * the idling option. 74 */ 75 void setActivityCount(int count) 76 { activityCount = count; } 77 78 /** Returns if the CPU should be active. */ 79 bool active() { return activityCount; } 80 81 /** Clears the time buffer and the activity count. */ 82 void reset(); 83 84 /** Debug function to dump the contents of the time buffer. */ 85 void dump(); 86 87 /** Debug function to ensure that the activity count matches the 88 * contents of the time buffer. 89 */ 90 void validate(); 91 92 private: 93 /** Time buffer that tracks if any cycles has active communication 94 * in them. It should be as long as the longest communication 95 * latency in the system. Each time any time buffer is written, 96 * the activity buffer should also be written to. The 97 * activityBuffer is advanced along with all the other time 98 * buffers, so it should have a 1 somewhere in it only if there 99 * is active communication in a time buffer. 100 */ 101 TimeBuffer<bool> activityBuffer; 102 103 /** Longest latency time buffer in the CPU. */ 104 int longestLatency; 105 106 /** Tracks how many stages and cycles of time buffer have 107 * activity. Stages increment this count when they switch to 108 * active, and decrement it when they switch to 109 * inactive. Whenever a cycle that previously had no information 110 * is written in the time buffer, this is incremented. When a 111 * cycle that had information exits the time buffer due to age, 112 * this count is decremented. When the count is 0, there is no 113 * activity in the CPU, and it can be descheduled. 114 */ 115 int activityCount; 116 117 /** Number of stages that can be marked as active or inactive. */ 118 int numStages; 119 120 /** Records which stages are active/inactive. */ 121 bool *stageActive; 122}; 123 124#endif // __CPU_ACTIVITY_HH__ 125