a368fba7d4
M5 skips over any simulated time where it doesn't have any work to do. When the simulation is active, the time skipped is short and the work done at any point in time is relatively substantial. If the time between events is long and/or the work to do at each event is small, it's possible for simulated time to pass faster than real time. When running a benchmark that can be good because it means the simulation will finish sooner in real time. When interacting with the real world through, for instance, a serial terminal or bridge to a real network, this can be a problem. Human or network response time could be greatly exagerated from the perspective of the simulation and make simulated events happen "too soon" from an external perspective. This change adds the capability to force the simulation to run no faster than real time. It does so by scheduling a periodic event that checks to see if its simulated period is shorter than its real period. If it is, it stalls the simulation until they're equal. This is called time syncing. A future change could add pseudo instructions which turn time syncing on and off from within the simulation. That would allow time syncing to be used for the interactive parts of a session but then turned off when running a benchmark using the m5 utility program inside a script. Time syncing would probably not happen anyway while running a benchmark because there would be plenty of work for M5 to do, but the event overhead could be avoided.
65 lines
2.8 KiB
Python
65 lines
2.8 KiB
Python
# Copyright (c) 2005-2007 The Regents of The University of Michigan
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# Copyright (c) 2010 Advanced Micro Devices, Inc.
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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: Nathan Binkert
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from m5.SimObject import SimObject
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from m5.params import *
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from m5.util import fatal
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class Root(SimObject):
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_the_instance = None
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def __new__(cls, **kwargs):
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if Root._the_instance:
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fatal("Attempt to allocate multiple instances of Root.")
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return None
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# first call: allocate the unique instance
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#
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# If SimObject ever implements __new__, we may want to pass
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# kwargs here, but for now this goes straight to
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# object.__new__ which prints an ugly warning if you pass it
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# args. Seems like a bad design but that's the way it is.
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Root._the_instance = SimObject.__new__(cls)
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return Root._the_instance
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@classmethod
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def getInstance(cls):
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return Root._the_instance
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def path(self):
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return 'root'
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type = 'Root'
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# Time syncing prevents the simulation from running faster than real time.
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time_sync_enable = Param.Bool(False, "whether time syncing is enabled")
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time_sync_period = Param.Clock("100ms", "how often to sync with real time")
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time_sync_spin_threshold = \
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Param.Clock("100us", "when less than this much time is left, spin")
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