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Diffstat (limited to 'src/cpu/activity.hh')
| -rw-r--r-- | src/cpu/activity.hh | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/src/cpu/activity.hh b/src/cpu/activity.hh new file mode 100644 index 000000000..e99927339 --- /dev/null +++ b/src/cpu/activity.hh @@ -0,0 +1,126 @@ +/* + * 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/timebuf.hh" +#include "base/trace.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(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: + /** 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__ |