1 // Copyright (c) 2012-present The Bitcoin Core developers
2 // Distributed under the MIT software license, see the accompanying
3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
4 5 #include <cuckoocache.h>
6 #include <random.h>
7 #include <script/sigcache.h>
8 #include <test/util/random.h>
9 #include <test/util/setup_common.h>
10 #include <util/byte_units.h>
11 12 #include <boost/test/unit_test.hpp>
13 14 #include <deque>
15 #include <mutex>
16 #include <shared_mutex>
17 #include <thread>
18 #include <vector>
19 20 /** Test Suite for CuckooCache
21 *
22 * 1. All tests should have a deterministic result (using insecure rand
23 * with deterministic seeds)
24 * 2. Some test methods are templated to allow for easier testing
25 * against new versions / comparing
26 * 3. Results should be treated as a regression test, i.e., did the behavior
27 * change significantly from what was expected. This can be OK, depending on
28 * the nature of the change, but requires updating the tests to reflect the new
29 * expected behavior. For example improving the hit rate may cause some tests
30 * using BOOST_CHECK_CLOSE to fail.
31 *
32 */
33 BOOST_FIXTURE_TEST_SUITE(cuckoocache_tests, BasicTestingSetup);
34 35 /* Test that no values not inserted into the cache are read out of it.
36 *
37 * There are no repeats in the first 200000 m_rng.rand256() calls
38 */
39 BOOST_AUTO_TEST_CASE(test_cuckoocache_no_fakes)
40 {
41 SeedRandomForTest(SeedRand::ZEROS);
42 CuckooCache::cache<uint256, SignatureCacheHasher> cc{};
43 cc.setup_bytes(4_MiB);
44 for (int x = 0; x < 100000; ++x) {
45 cc.insert(m_rng.rand256());
46 }
47 for (int x = 0; x < 100000; ++x) {
48 BOOST_CHECK(!cc.contains(m_rng.rand256(), false));
49 }
50 };
51 52 struct HitRateTest : BasicTestingSetup {
53 /** This helper returns the hit rate when bytes*load worth of entries are
54 * inserted into a bytes sized cache
55 */
56 template <typename Cache>
57 double test_cache(size_t bytes, double load)
58 {
59 SeedRandomForTest(SeedRand::ZEROS);
60 std::vector<uint256> hashes;
61 Cache set{};
62 set.setup_bytes(bytes);
63 uint32_t n_insert = static_cast<uint32_t>(load * (bytes / sizeof(uint256)));
64 hashes.resize(n_insert);
65 for (uint32_t i = 0; i < n_insert; ++i) {
66 uint32_t* ptr = (uint32_t*)hashes[i].begin();
67 for (uint8_t j = 0; j < 8; ++j)
68 *(ptr++) = m_rng.rand32();
69 }
70 /** We make a copy of the hashes because future optimizations of the
71 * cuckoocache may overwrite the inserted element, so the test is
72 * "future proofed".
73 */
74 std::vector<uint256> hashes_insert_copy = hashes;
75 /** Do the insert */
76 for (const uint256& h : hashes_insert_copy)
77 set.insert(h);
78 /** Count the hits */
79 uint32_t count = 0;
80 for (const uint256& h : hashes)
81 count += set.contains(h, false);
82 double hit_rate = ((double)count) / ((double)n_insert);
83 return hit_rate;
84 }
85 86 /** The normalized hit rate for a given load.
87 *
88 * The semantics are a little confusing, so please see the below
89 * explanation.
90 *
91 * Examples:
92 *
93 * 1. at load 0.5, we expect a perfect hit rate, so we multiply by
94 * 1.0
95 * 2. at load 2.0, we expect to see half the entries, so a perfect hit rate
96 * would be 0.5. Therefore, if we see a hit rate of 0.4, 0.4*2.0 = 0.8 is the
97 * normalized hit rate.
98 *
99 * This is basically the right semantics, but has a bit of a glitch depending on
100 * how you measure around load 1.0 as after load 1.0 your normalized hit rate
101 * becomes effectively perfect, ignoring freshness.
102 */
103 static double normalize_hit_rate(double hits, double load)
104 {
105 return hits * std::max(load, 1.0);
106 }
107 }; // struct HitRateTest
108 109 /** Check the hit rate on loads ranging from 0.1 to 1.6 */
110 BOOST_FIXTURE_TEST_CASE(cuckoocache_hit_rate_ok, HitRateTest)
111 {
112 /** Arbitrarily selected Hit Rate threshold that happens to work for this test
113 * as a lower bound on performance.
114 */
115 double HitRateThresh = 0.98;
116 for (double load = 0.1; load < 2; load *= 2) {
117 double hits = test_cache<CuckooCache::cache<uint256, SignatureCacheHasher>>(4_MiB, load);
118 BOOST_CHECK(normalize_hit_rate(hits, load) > HitRateThresh);
119 }
120 }
121 122 123 struct EraseTest : BasicTestingSetup {
124 /** This helper checks that erased elements are preferentially inserted onto and
125 * that the hit rate of "fresher" keys is reasonable*/
126 template <typename Cache>
127 void test_cache_erase(size_t bytes)
128 {
129 double load = 1;
130 SeedRandomForTest(SeedRand::ZEROS);
131 std::vector<uint256> hashes;
132 Cache set{};
133 set.setup_bytes(bytes);
134 uint32_t n_insert = static_cast<uint32_t>(load * (bytes / sizeof(uint256)));
135 hashes.resize(n_insert);
136 for (uint32_t i = 0; i < n_insert; ++i) {
137 uint32_t* ptr = (uint32_t*)hashes[i].begin();
138 for (uint8_t j = 0; j < 8; ++j)
139 *(ptr++) = m_rng.rand32();
140 }
141 /** We make a copy of the hashes because future optimizations of the
142 * cuckoocache may overwrite the inserted element, so the test is
143 * "future proofed".
144 */
145 std::vector<uint256> hashes_insert_copy = hashes;
146 147 /** Insert the first half */
148 for (uint32_t i = 0; i < (n_insert / 2); ++i)
149 set.insert(hashes_insert_copy[i]);
150 /** Erase the first quarter */
151 for (uint32_t i = 0; i < (n_insert / 4); ++i)
152 BOOST_CHECK(set.contains(hashes[i], true));
153 /** Insert the second half */
154 for (uint32_t i = (n_insert / 2); i < n_insert; ++i)
155 set.insert(hashes_insert_copy[i]);
156 157 /** elements that we marked as erased but are still there */
158 size_t count_erased_but_contained = 0;
159 /** elements that we did not erase but are older */
160 size_t count_stale = 0;
161 /** elements that were most recently inserted */
162 size_t count_fresh = 0;
163 164 for (uint32_t i = 0; i < (n_insert / 4); ++i)
165 count_erased_but_contained += set.contains(hashes[i], false);
166 for (uint32_t i = (n_insert / 4); i < (n_insert / 2); ++i)
167 count_stale += set.contains(hashes[i], false);
168 for (uint32_t i = (n_insert / 2); i < n_insert; ++i)
169 count_fresh += set.contains(hashes[i], false);
170 171 double hit_rate_erased_but_contained = double(count_erased_but_contained) / (double(n_insert) / 4.0);
172 double hit_rate_stale = double(count_stale) / (double(n_insert) / 4.0);
173 double hit_rate_fresh = double(count_fresh) / (double(n_insert) / 2.0);
174 175 // Check that our hit_rate_fresh is perfect
176 BOOST_CHECK_EQUAL(hit_rate_fresh, 1.0);
177 // Check that we have a more than 2x better hit rate on stale elements than
178 // erased elements.
179 BOOST_CHECK(hit_rate_stale > 2 * hit_rate_erased_but_contained);
180 }
181 }; // struct EraseTest
182 183 BOOST_FIXTURE_TEST_CASE(cuckoocache_erase_ok, EraseTest)
184 {
185 test_cache_erase<CuckooCache::cache<uint256, SignatureCacheHasher>>(4_MiB);
186 }
187 188 struct EraseParallelTest : BasicTestingSetup {
189 template <typename Cache>
190 void test_cache_erase_parallel(size_t bytes)
191 {
192 double load = 1;
193 SeedRandomForTest(SeedRand::ZEROS);
194 std::vector<uint256> hashes;
195 Cache set{};
196 set.setup_bytes(bytes);
197 uint32_t n_insert = static_cast<uint32_t>(load * (bytes / sizeof(uint256)));
198 hashes.resize(n_insert);
199 for (uint32_t i = 0; i < n_insert; ++i) {
200 uint32_t* ptr = (uint32_t*)hashes[i].begin();
201 for (uint8_t j = 0; j < 8; ++j)
202 *(ptr++) = m_rng.rand32();
203 }
204 /** We make a copy of the hashes because future optimizations of the
205 * cuckoocache may overwrite the inserted element, so the test is
206 * "future proofed".
207 */
208 std::vector<uint256> hashes_insert_copy = hashes;
209 std::shared_mutex mtx;
210 211 {
212 /** Grab lock to make sure we release inserts */
213 std::unique_lock<std::shared_mutex> l(mtx);
214 /** Insert the first half */
215 for (uint32_t i = 0; i < (n_insert / 2); ++i)
216 set.insert(hashes_insert_copy[i]);
217 }
218 219 /** Spin up 3 threads to run contains with erase.
220 */
221 std::vector<std::thread> threads;
222 threads.reserve(3);
223 /** Erase the first quarter */
224 for (uint32_t x = 0; x < 3; ++x)
225 /** Each thread is emplaced with x copy-by-value
226 */
227 threads.emplace_back([&, x] {
228 std::shared_lock<std::shared_mutex> l(mtx);
229 size_t ntodo = (n_insert/4)/3;
230 size_t start = ntodo*x;
231 size_t end = ntodo*(x+1);
232 for (uint32_t i = start; i < end; ++i) {
233 bool contains = set.contains(hashes[i], true);
234 assert(contains);
235 }
236 });
237 238 /** Wait for all threads to finish
239 */
240 for (std::thread& t : threads)
241 t.join();
242 /** Grab lock to make sure we observe erases */
243 std::unique_lock<std::shared_mutex> l(mtx);
244 /** Insert the second half */
245 for (uint32_t i = (n_insert / 2); i < n_insert; ++i)
246 set.insert(hashes_insert_copy[i]);
247 248 /** elements that we marked erased but that are still there */
249 size_t count_erased_but_contained = 0;
250 /** elements that we did not erase but are older */
251 size_t count_stale = 0;
252 /** elements that were most recently inserted */
253 size_t count_fresh = 0;
254 255 for (uint32_t i = 0; i < (n_insert / 4); ++i)
256 count_erased_but_contained += set.contains(hashes[i], false);
257 for (uint32_t i = (n_insert / 4); i < (n_insert / 2); ++i)
258 count_stale += set.contains(hashes[i], false);
259 for (uint32_t i = (n_insert / 2); i < n_insert; ++i)
260 count_fresh += set.contains(hashes[i], false);
261 262 double hit_rate_erased_but_contained = double(count_erased_but_contained) / (double(n_insert) / 4.0);
263 double hit_rate_stale = double(count_stale) / (double(n_insert) / 4.0);
264 double hit_rate_fresh = double(count_fresh) / (double(n_insert) / 2.0);
265 266 // Check that our hit_rate_fresh is perfect
267 BOOST_CHECK_EQUAL(hit_rate_fresh, 1.0);
268 // Check that we have a more than 2x better hit rate on stale elements than
269 // erased elements.
270 BOOST_CHECK(hit_rate_stale > 2 * hit_rate_erased_but_contained);
271 }
272 }; // struct EraseParallelTest
273 BOOST_FIXTURE_TEST_CASE(cuckoocache_erase_parallel_ok, EraseParallelTest)
274 {
275 test_cache_erase_parallel<CuckooCache::cache<uint256, SignatureCacheHasher>>(4_MiB);
276 }
277 278 279 struct GenerationsTest : BasicTestingSetup {
280 template <typename Cache>
281 void test_cache_generations()
282 {
283 // This test checks that for a simulation of network activity, the fresh hit
284 // rate is never below 99%, and the number of times that it is worse than
285 // 99.9% are less than 1% of the time.
286 double min_hit_rate = 0.99;
287 double tight_hit_rate = 0.999;
288 double max_rate_less_than_tight_hit_rate = 0.01;
289 // A cache that meets this specification is therefore shown to have a hit
290 // rate of at least tight_hit_rate * (1 - max_rate_less_than_tight_hit_rate) +
291 // min_hit_rate*max_rate_less_than_tight_hit_rate = 0.999*99%+0.99*1% == 99.89%
292 // hit rate with low variance.
293 294 // We use deterministic values, but this test has also passed on many
295 // iterations with non-deterministic values, so it isn't "overfit" to the
296 // specific entropy in FastRandomContext(true) and implementation of the
297 // cache.
298 SeedRandomForTest(SeedRand::ZEROS);
299 300 // block_activity models a chunk of network activity. n_insert elements are
301 // added to the cache. The first and last n/4 are stored for removal later
302 // and the middle n/2 are not stored. This models a network which uses half
303 // the signatures of recently (since the last block) added transactions
304 // immediately and never uses the other half.
305 struct block_activity {
306 std::vector<uint256> reads;
307 block_activity(uint32_t n_insert, FastRandomContext& rng, Cache& c)
308 {
309 std::vector<uint256> inserts;
310 inserts.resize(n_insert);
311 reads.reserve(n_insert / 2);
312 for (uint32_t i = 0; i < n_insert; ++i) {
313 uint32_t* ptr = (uint32_t*)inserts[i].begin();
314 for (uint8_t j = 0; j < 8; ++j)
315 *(ptr++) = rng.rand32();
316 }
317 for (uint32_t i = 0; i < n_insert / 4; ++i)
318 reads.push_back(inserts[i]);
319 for (uint32_t i = n_insert - (n_insert / 4); i < n_insert; ++i)
320 reads.push_back(inserts[i]);
321 for (const auto& h : inserts)
322 c.insert(h);
323 }
324 };
325 326 const uint32_t BLOCK_SIZE = 1000;
327 // We expect window size 60 to perform reasonably given that each epoch
328 // stores 45% of the cache size (~472k).
329 const uint32_t WINDOW_SIZE = 60;
330 const uint32_t POP_AMOUNT = (BLOCK_SIZE / WINDOW_SIZE) / 2;
331 const double load = 10;
332 const size_t bytes{4_MiB};
333 const uint32_t n_insert = static_cast<uint32_t>(load * (bytes / sizeof(uint256)));
334 335 std::vector<block_activity> hashes;
336 Cache set{};
337 set.setup_bytes(bytes);
338 hashes.reserve(n_insert / BLOCK_SIZE);
339 std::deque<block_activity> last_few;
340 uint32_t out_of_tight_tolerance = 0;
341 uint32_t total = n_insert / BLOCK_SIZE;
342 // we use the deque last_few to model a sliding window of blocks. at each
343 // step, each of the last WINDOW_SIZE block_activities checks the cache for
344 // POP_AMOUNT of the hashes that they inserted, and marks these erased.
345 for (uint32_t i = 0; i < total; ++i) {
346 if (last_few.size() == WINDOW_SIZE)
347 last_few.pop_front();
348 last_few.emplace_back(BLOCK_SIZE, m_rng, set);
349 uint32_t count = 0;
350 for (auto& act : last_few)
351 for (uint32_t k = 0; k < POP_AMOUNT; ++k) {
352 count += set.contains(act.reads.back(), true);
353 act.reads.pop_back();
354 }
355 // We use last_few.size() rather than WINDOW_SIZE for the correct
356 // behavior on the first WINDOW_SIZE iterations where the deque is not
357 // full yet.
358 double hit = (double(count)) / (last_few.size() * POP_AMOUNT);
359 // Loose Check that hit rate is above min_hit_rate
360 BOOST_CHECK(hit > min_hit_rate);
361 // Tighter check, count number of times we are less than tight_hit_rate
362 // (and implicitly, greater than min_hit_rate)
363 out_of_tight_tolerance += hit < tight_hit_rate;
364 }
365 // Check that being out of tolerance happens less than
366 // max_rate_less_than_tight_hit_rate of the time
367 BOOST_CHECK(double(out_of_tight_tolerance) / double(total) < max_rate_less_than_tight_hit_rate);
368 }
369 }; // struct GenerationsTest
370 BOOST_FIXTURE_TEST_CASE(cuckoocache_generations, GenerationsTest)
371 {
372 test_cache_generations<CuckooCache::cache<uint256, SignatureCacheHasher>>();
373 }
374 375 BOOST_AUTO_TEST_SUITE_END();
376