mem: Rework the structuring of the prefetchers

Re-organizes the prefetcher class structure. Previously the
BasePrefetcher forced multiple assumptions on the prefetchers that
inherited from it. This patch makes the BasePrefetcher class truly
representative of base functionality. For example, the base class no
longer enforces FIFO order. Instead, prefetchers with FIFO requests
(like the existing stride and tagged prefetchers) now inherit from a
new QueuedPrefetcher base class.

Finally, the stride-based prefetcher now assumes a custimizable lookup table
(sets/ways) rather than the previous fully associative structure.

1 files changed, 213 insertions, 0 deletions

diff --git a/src/mem/cache/prefetch/queued.cc b/src/mem/cache/prefetch/queued.cc
new file mode 100644
index 000000000..318d565dc
--- /dev/null
+++ b/src/mem/cache/prefetch/queued.cc
@@ -0,0 +1,213 @@
+/*
+ * Copyright (c) 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: Mitch Hayenga
+ */
+
+#include "debug/HWPrefetch.hh"
+#include "mem/cache/prefetch/queued.hh"
+#include "mem/cache/base.hh"
+
+QueuedPrefetcher::QueuedPrefetcher(const QueuedPrefetcherParams *p)
+    : BasePrefetcher(p), queueSize(p->queue_size), latency(p->latency),
+      queueSquash(p->queue_squash), queueFilter(p->queue_filter),
+      cacheSnoop(p->cache_snoop), tagPrefetch(p->tag_prefetch)
+{
+
+}
+
+QueuedPrefetcher::~QueuedPrefetcher()
+{
+    // Delete the queued prefetch packets
+    for (DeferredPacket &p : pfq) {
+        delete p.pkt->req;
+        delete p.pkt;
+    }
+}
+
+Tick
+QueuedPrefetcher::notify(const PacketPtr &pkt)
+{
+    // Verify this access type is observed by prefetcher
+    if (observeAccess(pkt)) {
+        Addr blk_addr = pkt->getAddr() & ~(Addr)(blkSize - 1);
+        bool is_secure = pkt->isSecure();
+
+        // Squash queued prefetches if demand miss to same line
+        if (queueSquash) {
+            auto itr = pfq.begin();
+            while (itr != pfq.end()) {
+                if (itr->pkt->getAddr() == blk_addr &&
+                    itr->pkt->isSecure() == is_secure) {
+                    delete itr->pkt->req;
+                    delete itr->pkt;
+                    itr = pfq.erase(itr);
+                } else {
+                    ++itr;
+                }
+            }
+
+            if (pfq.empty())
+                cache->deassertMemSideBusRequest(BaseCache::Request_PF);
+        }
+
+        // Calculate prefetches given this access
+        std::vector<Addr> addresses;
+        calculatePrefetch(pkt, addresses);
+
+        // Queue up generated prefetches
+        for (Addr pf_addr : addresses) {
+
+            // Block align prefetch address
+            pf_addr = pf_addr & ~(Addr)(blkSize - 1);
+
+            pfIdentified++;
+            DPRINTF(HWPrefetch, "Found a pf candidate addr: %#x, "
+                    "inserting into prefetch queue.\n", pf_addr);
+
+            if (queueFilter && inPrefetch(pf_addr, is_secure)) {
+                pfBufferHit++;
+                DPRINTF(HWPrefetch, "Prefetch addr already in "
+                        "prefetch queue\n");
+                continue;
+            }
+
+            if (cacheSnoop && (inCache(pf_addr, is_secure) ||
+                        inMissQueue(pf_addr, is_secure))) {
+                pfInCache++;
+                DPRINTF(HWPrefetch, "Dropping redundant in "
+                        "cache/MSHR prefetch addr:%#x\n", pf_addr);
+                continue;
+            }
+
+            // Create a prefetch memory request
+            Request *pf_req =
+                new Request(pf_addr, blkSize, 0, masterId);
+
+            if (is_secure) {
+                pf_req->setFlags(Request::SECURE);
+            }
+            pf_req->taskId(ContextSwitchTaskId::Prefetcher);
+            PacketPtr pf_pkt = new Packet(pf_req, MemCmd::HardPFReq);
+            pf_pkt->allocate();
+
+            if (pkt->req->hasContextId()) {
+                pf_req->setThreadContext(pkt->req->contextId(),
+                                         pkt->req->threadId());
+            }
+
+            if (tagPrefetch && pkt->req->hasPC()) {
+                // Tag prefetch packet with  accessing pc
+                pf_pkt->req->setPC(pkt->req->getPC());
+            }
+
+            // Verify prefetch buffer space for request
+            if (pfq.size() == queueSize) {
+                pfRemovedFull++;
+                PacketPtr old_pkt = pfq.begin()->pkt;
+                DPRINTF(HWPrefetch, "Prefetch queue full, removing "
+                        "oldest packet addr: %#x", old_pkt->getAddr());
+                delete old_pkt->req;
+                delete old_pkt;
+                pfq.pop_front();
+            }
+
+            Tick pf_time = curTick() + clockPeriod() * latency;
+            DPRINTF(HWPrefetch, "Prefetch queued. "
+                    "addr:%#x tick:%lld.\n", pf_addr, pf_time);
+
+            pfq.push_back(DeferredPacket(pf_time, pf_pkt));
+        }
+    }
+
+    return pfq.empty() ? MaxTick : pfq.front().tick;
+}
+
+PacketPtr
+QueuedPrefetcher::getPacket()
+{
+    DPRINTF(HWPrefetch, "Requesting a prefetch to issue.\n");
+
+    if (pfq.empty()) {
+        DPRINTF(HWPrefetch, "No hardware prefetches available.\n");
+        return NULL;
+    }
+
+    PacketPtr pkt = pfq.begin()->pkt;
+    pfq.pop_front();
+
+    pfIssued++;
+    assert(pkt != NULL);
+    DPRINTF(HWPrefetch, "Generating prefetch for %#x.\n", pkt->getAddr());
+    return pkt;
+}
+
+bool
+QueuedPrefetcher::inPrefetch(Addr address, bool is_secure) const
+{
+    for (const DeferredPacket &dp : pfq) {
+        if (dp.pkt->getAddr() == address &&
+            dp.pkt->isSecure() == is_secure) return true;
+    }
+
+    return false;
+}
+
+void
+QueuedPrefetcher::regStats()
+{
+    BasePrefetcher::regStats();
+
+    pfIdentified
+        .name(name() + ".pfIdentified")
+        .desc("number of prefetch candidates identified");
+
+    pfBufferHit
+        .name(name() + ".pfBufferHit")
+        .desc("number of redundant prefetches already in prefetch queue");
+
+    pfInCache
+        .name(name() + ".pfInCache")
+        .desc("number of redundant prefetches already in cache/mshr dropped");
+
+    pfRemovedFull
+        .name(name() + ".pfRemovedFull")
+        .desc("number of prefetches dropped due to prefetch queue size");
+
+    pfSpanPage
+        .name(name() + ".pfSpanPage")
+        .desc("number of prefetches not generated due to page crossing");
+}