1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
|
/*
* Copyright (c) 2006 The Regents of The University of Michigan
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Kevin Lim
*/
#ifndef __CPU_ACTIVITY_HH__
#define __CPU_ACTIVITY_HH__
#include "base/trace.hh"
#include "cpu/timebuf.hh"
/**
* ActivityRecorder helper class that informs the CPU if it can switch
* over to being idle or not. It works by having a time buffer as
* long as any time buffer in the CPU, and the CPU and all of its
* stages inform the ActivityRecorder when they write to any time
* buffer. The ActivityRecorder marks a 1 in the "0" slot of the time
* buffer any time a stage writes to a time buffer, and it advances
* its time buffer at the same time as all other stages. The
* ActivityRecorder also records if a stage has activity to do next
* cycle. The recorder keeps a count of these two. Thus any time the
* count is non-zero, there is either communication still in flight,
* or activity that still must be done, meaning that the CPU can not
* idle. If count is zero, then the CPU can safely idle as it has no
* more outstanding work to do.
*/
class ActivityRecorder
{
public:
ActivityRecorder(const std::string &name, int num_stages,
int longest_latency, int count);
/** Records that there is activity this cycle. */
void activity();
/** Advances the activity buffer, decrementing the activityCount
* if active communication just left the time buffer, and
* determining if there is no activity.
*/
void advance();
/** Marks a stage as active. */
void activateStage(const int idx);
/** Deactivates a stage. */
void deactivateStage(const int idx);
/** Returns how many things are active within the recorder. */
int getActivityCount() { return activityCount; }
/** Sets the count to a starting value. Can be used to disable
* the idling option.
*/
void setActivityCount(int count)
{ activityCount = count; }
/** Returns if the CPU should be active. */
bool active() { return activityCount; }
/** Clears the time buffer and the activity count. */
void reset();
/** Debug function to dump the contents of the time buffer. */
void dump();
/** Debug function to ensure that the activity count matches the
* contents of the time buffer.
*/
void validate();
private:
// provide name() for DPRINTF.
std::string _name;
const std::string &name() { return _name; }
/** Time buffer that tracks if any cycles has active communication
* in them. It should be as long as the longest communication
* latency in the system. Each time any time buffer is written,
* the activity buffer should also be written to. The
* activityBuffer is advanced along with all the other time
* buffers, so it should have a 1 somewhere in it only if there
* is active communication in a time buffer.
*/
TimeBuffer<bool> activityBuffer;
/** Longest latency time buffer in the CPU. */
int longestLatency;
/** Tracks how many stages and cycles of time buffer have
* activity. Stages increment this count when they switch to
* active, and decrement it when they switch to
* inactive. Whenever a cycle that previously had no information
* is written in the time buffer, this is incremented. When a
* cycle that had information exits the time buffer due to age,
* this count is decremented. When the count is 0, there is no
* activity in the CPU, and it can be descheduled.
*/
int activityCount;
/** Number of stages that can be marked as active or inactive. */
int numStages;
/** Records which stages are active/inactive. */
bool *stageActive;
};
#endif // __CPU_ACTIVITY_HH__
|
