base_set_assoc.hh revision 13419:aaadcfae091a 
1/*
2 * Copyright (c) 2012-2014,2017 ARM Limited
3 * All rights reserved.
4 *
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8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder.  You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2003-2005,2014 The Regents of The University of Michigan
15 * All rights reserved.
16 *
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18 * modification, are permitted provided that the following conditions are
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26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Erik Hallnor
41 */
42
43/**
44 * @file
45 * Declaration of a base set associative tag store.
46 */
47
48#ifndef __MEM_CACHE_TAGS_BASE_SET_ASSOC_HH__
49#define __MEM_CACHE_TAGS_BASE_SET_ASSOC_HH__
50
51#include <functional>
52#include <string>
53#include <vector>
54
55#include "base/logging.hh"
56#include "base/types.hh"
57#include "mem/cache/base.hh"
58#include "mem/cache/cache_blk.hh"
59#include "mem/cache/replacement_policies/base.hh"
60#include "mem/cache/replacement_policies/replaceable_entry.hh"
61#include "mem/cache/tags/base.hh"
62#include "mem/cache/tags/indexing_policies/base.hh"
63#include "params/BaseSetAssoc.hh"
64
65/**
66 * A basic cache tag store.
67 * @sa  \ref gem5MemorySystem "gem5 Memory System"
68 *
69 * The BaseSetAssoc placement policy divides the cache into s sets of w
70 * cache lines (ways).
71 */
72class BaseSetAssoc : public BaseTags
73{
74  protected:
75    /** The allocatable associativity of the cache (alloc mask). */
76    unsigned allocAssoc;
77
78    /** The cache blocks. */
79    std::vector<CacheBlk> blks;
80
81    /** Whether tags and data are accessed sequentially. */
82    const bool sequentialAccess;
83
84    /** Replacement policy */
85    BaseReplacementPolicy *replacementPolicy;
86
87  public:
88    /** Convenience typedef. */
89     typedef BaseSetAssocParams Params;
90
91    /**
92     * Construct and initialize this tag store.
93     */
94    BaseSetAssoc(const Params *p);
95
96    /**
97     * Destructor
98     */
99    virtual ~BaseSetAssoc() {};
100
101    /**
102     * Initialize blocks as CacheBlk instances.
103     */
104    void tagsInit() override;
105
106    /**
107     * This function updates the tags when a block is invalidated. It also
108     * updates the replacement data.
109     *
110     * @param blk The block to invalidate.
111     */
112    void invalidate(CacheBlk *blk) override;
113
114    /**
115     * Access block and update replacement data. May not succeed, in which case
116     * nullptr is returned. This has all the implications of a cache access and
117     * should only be used as such. Returns the tag lookup latency as a side
118     * effect.
119     *
120     * @param addr The address to find.
121     * @param is_secure True if the target memory space is secure.
122     * @param lat The latency of the tag lookup.
123     * @return Pointer to the cache block if found.
124     */
125    CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat) override
126    {
127        CacheBlk *blk = findBlock(addr, is_secure);
128
129        // Access all tags in parallel, hence one in each way.  The data side
130        // either accesses all blocks in parallel, or one block sequentially on
131        // a hit.  Sequential access with a miss doesn't access data.
132        tagAccesses += allocAssoc;
133        if (sequentialAccess) {
134            if (blk != nullptr) {
135                dataAccesses += 1;
136            }
137        } else {
138            dataAccesses += allocAssoc;
139        }
140
141        // If a cache hit
142        if (blk != nullptr) {
143            // Update number of references to accessed block
144            blk->refCount++;
145
146            // Update replacement data of accessed block
147            replacementPolicy->touch(blk->replacementData);
148        }
149
150        // The tag lookup latency is the same for a hit or a miss
151        lat = lookupLatency;
152
153        return blk;
154    }
155
156    /**
157     * Find replacement victim based on address. The list of evicted blocks
158     * only contains the victim.
159     *
160     * @param addr Address to find a victim for.
161     * @param is_secure True if the target memory space is secure.
162     * @param evict_blks Cache blocks to be evicted.
163     * @return Cache block to be replaced.
164     */
165    CacheBlk* findVictim(Addr addr, const bool is_secure,
166                         std::vector<CacheBlk*>& evict_blks) const override
167    {
168        // Get possible entries to be victimized
169        const std::vector<ReplaceableEntry*> entries =
170            indexingPolicy->getPossibleEntries(addr);
171
172        // Choose replacement victim from replacement candidates
173        CacheBlk* victim = static_cast<CacheBlk*>(replacementPolicy->getVictim(
174                                entries));
175
176        // There is only one eviction for this replacement
177        evict_blks.push_back(victim);
178
179        return victim;
180    }
181
182    /**
183     * Insert the new block into the cache and update replacement data.
184     *
185     * @param addr Address of the block.
186     * @param is_secure Whether the block is in secure space or not.
187     * @param src_master_ID The source requestor ID.
188     * @param task_ID The new task ID.
189     * @param blk The block to update.
190     */
191    void insertBlock(const Addr addr, const bool is_secure,
192                     const int src_master_ID, const uint32_t task_ID,
193                     CacheBlk *blk) override
194    {
195        // Insert block
196        BaseTags::insertBlock(addr, is_secure, src_master_ID, task_ID, blk);
197
198        // Increment tag counter
199        tagsInUse++;
200
201        // Update replacement policy
202        replacementPolicy->reset(blk->replacementData);
203    }
204
205    /**
206     * Limit the allocation for the cache ways.
207     * @param ways The maximum number of ways available for replacement.
208     */
209    virtual void setWayAllocationMax(int ways) override
210    {
211        fatal_if(ways < 1, "Allocation limit must be greater than zero");
212        allocAssoc = ways;
213    }
214
215    /**
216     * Get the way allocation mask limit.
217     * @return The maximum number of ways available for replacement.
218     */
219    virtual int getWayAllocationMax() const override
220    {
221        return allocAssoc;
222    }
223
224    /**
225     * Regenerate the block address from the tag and indexing location.
226     *
227     * @param block The block.
228     * @return the block address.
229     */
230    Addr regenerateBlkAddr(const CacheBlk* blk) const override
231    {
232        return indexingPolicy->regenerateAddr(blk->tag, blk);
233    }
234
235    void forEachBlk(std::function<void(CacheBlk &)> visitor) override {
236        for (CacheBlk& blk : blks) {
237            visitor(blk);
238        }
239    }
240
241    bool anyBlk(std::function<bool(CacheBlk &)> visitor) override {
242        for (CacheBlk& blk : blks) {
243            if (visitor(blk)) {
244                return true;
245            }
246        }
247        return false;
248    }
249};
250
251#endif //__MEM_CACHE_TAGS_BASE_SET_ASSOC_HH__
252