power: Add basic DVFS support for gem5

Adds DVFS capabilities to gem5, by allowing users to specify lists for
frequencies and voltages in SrcClockDomains and VoltageDomains respectively.
A separate component, DVFSHandler, provides a small interface to change
operating points of the associated domains.

Clock domains will be linked to voltage domains and thus allow separate clock,
but shared voltage lines.

Currently all the valid performance-level updates are performed with a fixed
transition latency as specified for the domain.

Config file example:
...
vd = VoltageDomain(voltage = ['1V','0.95V','0.90V','0.85V'])
tsys.cluster1.clk_domain.clock = ['1GHz','700MHz','400MHz','230MHz']
tsys.cluster2.clk_domain.clock = ['1GHz','700MHz','400MHz','230MHz']
tsys.cluster1.clk_domain.domain_id = 0
tsys.cluster2.clk_domain.domain_id = 1
tsys.cluster1.clk_domain.voltage_domain = vd
tsys.cluster2.clk_domain.voltage_domain = vd
tsys.dvfs_handler.domains = [tsys.cluster1.clk_domain,
                             tsys.cluster2.clk_domain]
tsys.dvfs_handler.enable = True

1 files changed, 216 insertions, 0 deletions

diff --git a/src/sim/dvfs_handler.cc b/src/sim/dvfs_handler.cc
new file mode 100644
index 000000000..bb60b1850
--- /dev/null
+++ b/src/sim/dvfs_handler.cc
@@ -0,0 +1,216 @@
+/*
+ * Copyright (c) 2013-2014 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: Vasileios Spiliopoulos
+ *          Akash Bagdia
+ *          Stephan Diestelhorst
+ */
+
+#include <set>
+#include <utility>
+
+#include "base/misc.hh"
+#include "debug/DVFS.hh"
+#include "params/DVFSHandler.hh"
+#include "sim/clock_domain.hh"
+#include "sim/dvfs_handler.hh"
+#include "sim/stat_control.hh"
+#include "sim/voltage_domain.hh"
+
+//
+//
+// DVFSHandler methods implementation
+//
+
+DVFSHandler::DVFSHandler(const Params *p)
+    : SimObject(p),
+      sysClkDomain(p->sys_clk_domain),
+      enableHandler(p->enable),
+      _transLatency(p->transition_latency)
+{
+    // Check supplied list of domains for sanity and add them to the
+    // domain ID -> domain* hash
+    for(auto dit = p->domains.begin(); dit != p->domains.end(); ++dit) {
+        SrcClockDomain *d = *dit;
+        DomainID domain_id = d->domainID();
+
+        fatal_if(sysClkDomain == d, "DVFS: Domain config list has a "\
+                 "system clk domain entry");
+        fatal_if(domain_id == SrcClockDomain::emptyDomainID,
+                 "DVFS: Controlled domain %s needs to have a properly "\
+                 " assigned ID.\n", d->name());
+
+        auto entry = std::make_pair(domain_id, d);
+        bool new_elem = domains.insert(entry).second;
+        fatal_if(!new_elem, "DVFS: Domain %s with ID %d does not have a "\
+                 "unique ID.\n", d->name(), domain_id);
+
+        // Create a dedicated event slot per known domain ID
+        UpdateEvent *event = &updatePerfLevelEvents[domain_id];
+        event->domainIDToSet = d->domainID();
+    }
+    UpdateEvent::dvfsHandler = this;
+}
+
+DVFSHandler *DVFSHandler::UpdateEvent::dvfsHandler;
+
+bool
+DVFSHandler::validDomainID(DomainID domain_id) const
+{
+    assert(isEnabled());
+    // This is ensure that the domain id as requested by the software is
+    // availabe in the handler.
+    if (domains.find(domain_id) != domains.end())
+        return true;
+    warn("DVFS: invalid domain ID %d, the DVFS handler does not handle this "\
+         "domain\n", domain_id);
+    return false;
+}
+
+bool
+DVFSHandler::perfLevel(DomainID domain_id, PerfLevel perf_level)
+{
+    assert(isEnabled());
+
+    DPRINTF(DVFS, "DVFS: setPerfLevel domain %d -> %d\n", domain_id, perf_level);
+
+    auto d = findDomain(domain_id);
+    if (!d->validPerfLevel(perf_level)) {
+        warn("DVFS: invalid performance level %d for domain ID %d, request "\
+             "ignored\n", perf_level, domain_id);
+        return false;
+    }
+
+    UpdateEvent *update_event = &updatePerfLevelEvents[domain_id];
+    // Drop an old DVFS change request once we have established that this is a
+    // reasonable request
+    if (update_event->scheduled()) {
+        DPRINTF(DVFS, "DVFS: Overwriting the previous DVFS event.\n");
+        deschedule(update_event);
+    }
+
+    update_event->perfLevelToSet = perf_level;
+
+    // State changes that restore to the current state (and / or overwrite a not
+    // yet completed in-flight request) will be squashed
+    if (d->perfLevel() == perf_level) {
+        DPRINTF(DVFS, "DVFS: Ignoring ineffective performance level change "\
+                "%d -> %d\n", d->perfLevel(), perf_level);
+        return false;
+    }
+
+    // At this point, a new transition will certainly take place -> schedule
+    Tick when = curTick() + _transLatency;
+    DPRINTF(DVFS, "DVFS: Update for perf event scheduled for %ld\n", when);
+
+    schedule(update_event, when);
+    return true;
+}
+
+void
+DVFSHandler::UpdateEvent::updatePerfLevel()
+{
+    // Perform explicit stats dump for power estimation before performance
+    // level migration
+    Stats::dump();
+    Stats::reset();
+
+    // Update the performance level in the clock domain
+    auto d = dvfsHandler->findDomain(domainIDToSet);
+    assert(d->perfLevel() != perfLevelToSet);
+
+    d->perfLevel(perfLevelToSet);
+}
+
+void
+DVFSHandler::serialize(std::ostream &os)
+{
+    //This is to ensure that the handler status is maintained during the
+    //entire simulation run and not changed from command line during checkpoint
+    //and restore
+    SERIALIZE_SCALAR(enableHandler);
+
+    // Pull out the hashed data structure into easy-to-serialise arrays;
+    // ensuring that the data associated with any pending update event is saved
+    std::vector<DomainID> domain_ids;
+    std::vector<PerfLevel> perf_levels;
+    std::vector<Tick> whens;
+    for (auto it = updatePerfLevelEvents.begin();
+         it != updatePerfLevelEvents.end(); ++it) {
+        DomainID id = it->first;
+        UpdateEvent *event = &it->second;
+
+        assert(id == event->domainIDToSet);
+        domain_ids.push_back(id);
+        perf_levels.push_back(event->perfLevelToSet);
+        whens.push_back(event->scheduled() ? event->when() : 0);
+    }
+    arrayParamOut(os, "domain_ids", domain_ids);
+    arrayParamOut(os, "perf_levels", perf_levels);
+    arrayParamOut(os, "whens", whens);
+}
+
+void
+DVFSHandler::unserialize(Checkpoint *cp, const std::string &section)
+{
+    UNSERIALIZE_SCALAR(enableHandler);
+
+    // Reconstruct the map of domain IDs and their scheduled events
+    std::vector<DomainID> domain_ids;
+    std::vector<PerfLevel> perf_levels;
+    std::vector<Tick> whens;
+    arrayParamIn(cp, section, "domain_ids", domain_ids);
+    arrayParamIn(cp, section, "perf_levels", perf_levels);
+    arrayParamIn(cp, section, "whens", whens);
+
+    for (size_t i = 0; i < domain_ids.size(); ++i) {;
+        UpdateEvent *event = &updatePerfLevelEvents[domain_ids[i]];
+
+        event->domainIDToSet = domain_ids[i];
+        event->perfLevelToSet = perf_levels[i];
+
+        // Schedule all previously scheduled events
+        if (whens[i])
+            schedule(event, whens[i]);
+    }
+    UpdateEvent::dvfsHandler = this;
+}
+
+DVFSHandler*
+DVFSHandlerParams::create()
+{
+    return new DVFSHandler(this);
+}