MEM: Add the communication monitor

This patch adds a communication monitor MemObject that can be inserted
between a master and slave port to provide a range of statistics about
the communication passing through it. The communication monitor is
non-invasive and does not change any properties or timing of the
packets, with the exception of adding a sender state to be able to
track latency. The statistics are only collected in timing mode (not
atomic) to avoid slowing down any fast forwarding.

An example of the statistics captured by the monitor are: read/write
burst lengths, bandwidth, request-response latency, outstanding
transactions, inter transaction time, transaction count, and address
distribution. The monitor can be used in combination with periodic
resetting and dumping of stats (through schedStatEvent) to study the
behaviour over time.

In future patches, a selection of convenience scripts will be added to
aid in visualising the statistics collected by the monitor.

1 files changed, 97 insertions, 0 deletions

diff --git a/src/mem/CommMonitor.py b/src/mem/CommMonitor.py
new file mode 100644
index 000000000..3621942d9
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+++ b/src/mem/CommMonitor.py
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+# Copyright (c) 2012 ARM Limited
+# All rights reserved.
+#
+# The license below extends only to copyright in the software and shall
+# not be construed as granting a license to any other intellectual
+# property including but not limited to intellectual property relating
+# to a hardware implementation of the functionality of the software
+# licensed hereunder.  You may use the software subject to the license
+# terms below provided that you ensure that this notice is replicated
+# unmodified and in its entirety in all distributions of the software,
+# modified or unmodified, in source code or in binary form.
+#
+# 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: Thomas Grass
+#          Andreas Hansson
+
+from m5.params import *
+from MemObject import MemObject
+
+# The communication monitor will most typically be used in combination
+# with periodic dumping and resetting of stats using schedStatEvent
+class CommMonitor(MemObject):
+    type = 'CommMonitor'
+
+    # one port in each direction
+    master = MasterPort("Master port")
+    slave = SlavePort("Slave port")
+
+    # control the sample period window length of this monitor
+    sample_period = Param.Clock("1ms", "Sample period for histograms")
+
+    # for each histogram, set the number of bins and enable the user
+    # to disable the measurement, reads and writes use the same
+    # parameters
+
+    # histogram of burst length of packets (not using sample period)
+    burst_length_bins = Param.Unsigned('20', "# bins in burst length " \
+                                           "histograms")
+    disable_burst_length_hists = Param.Bool(False, "Disable burst length " \
+                                                "histograms")
+
+    # bandwidth per sample period
+    bandwidth_bins = Param.Unsigned('20', "# bins in bandwidth histograms")
+    disable_bandwidth_hists = Param.Bool(False, "Disable bandwidth histograms")
+
+    # latency from request to response (not using sample period)
+    latency_bins = Param.Unsigned('20', "# bins in latency histograms")
+    disable_latency_hists = Param.Bool(False, "Disable latency histograms")
+
+    # inter transaction time (ITT) distributions in uniformly sized
+    # bins up to the maximum, independently for read-to-read,
+    # write-to-write and the combined request-to-request that does not
+    # separate read and write requests
+    itt_bins = Param.Unsigned('20', "# bins in ITT distributions")
+    itt_max_bin = Param.Latency('100ns', "Max bin of ITT distributions")
+    disable_itt_dists = Param.Bool(False, "Disable ITT distributions")
+
+    # outstanding requests (that did not yet get a response) per
+    # sample period
+    outstanding_bins = Param.Unsigned('20', "# bins in outstanding " \
+                                          "requests histograms")
+    disable_outstanding_hists = Param.Bool(False, "Disable outstanding " \
+                                               "requests histograms")
+
+    # transactions (requests) observed per sample period
+    transaction_bins = Param.Unsigned('20', "# bins in transaction " \
+                                          "count histograms")
+    disable_transaction_hists = Param.Bool(False, "Disable transaction count " \
+                                               "histograms")
+
+    # address distributions (heatmaps) with associated address masks
+    # to selectively only look at certain bits of the address
+    read_addr_mask = Param.Addr(MaxAddr, "Address mask for read address")
+    write_addr_mask = Param.Addr(MaxAddr, "Address mask for write address")
+    disable_addr_dists = Param.Bool(True, "Disable address distributions")