Merge pull request #11 from chenhao-ye/access_mode

Support Access Mode
chenhao-ye · Dec 2, 2023 · 003a49f · 003a49f
2 parents 76d21c2 + 9a03ece
commit 003a49f
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Showing 2 changed files with 71 additions and 15 deletions.
diff --git a/include/gcache/ghost_cache.h b/include/gcache/ghost_cache.h
@@ -15,6 +15,14 @@
 
 namespace gcache {
 
+// AccessMode controls the behavior to update cache stat
+enum AccessMode : uint8_t {
+  DEFAULT,  // update normally
+  AS_MISS,  // consider it as a miss for all cache sizes
+  AS_HIT,   // consider it as a hit for all cache sizes
+  NOOP,     // do not update
+};
+
 struct CacheStat {
   uint64_t hit_cnt;
   uint64_t miss_cnt;
@@ -77,7 +85,7 @@ class GhostCache {
   std::vector<Node_t*> size_boundaries;
   std::vector<CacheStat> caches_stat;
 
-  void access_impl(uint32_t block_id, uint32_t hash);
+  void access_impl(uint32_t block_id, uint32_t hash, AccessMode mode);
 
  public:
   GhostCache(uint32_t tick, uint32_t min_size, uint32_t max_size)
@@ -94,7 +102,9 @@ class GhostCache {
     assert(min_size + (num_ticks - 1) * tick == max_size);
     cache.init(max_size);
   }
-  void access(uint32_t block_id) { access_impl(block_id, ghash{}(block_id)); }
+  void access(uint32_t block_id, AccessMode mode = AccessMode::DEFAULT) {
+    access_impl(block_id, ghash{}(block_id), mode);
+  }
 
   [[nodiscard]] uint32_t get_tick() const { return tick; }
   [[nodiscard]] uint32_t get_min_size() const { return min_size; }
@@ -141,9 +151,9 @@ class SampledGhostCache : public GhostCache {
   }
 
   // Only update ghost cache if the first few bits of hash is all zero
-  void access(uint32_t block_id) {
+  void access(uint32_t block_id, AccessMode mode = AccessMode::DEFAULT) {
     uint32_t hash = ghash{}(block_id);
-    if ((hash >> (32 - SampleShift)) == 0) access_impl(block_id, hash);
+    if ((hash >> (32 - SampleShift)) == 0) access_impl(block_id, hash, mode);
   }
 
   uint32_t get_tick() const { return tick << SampleShift; }
@@ -168,7 +178,8 @@ class SampledGhostCache : public GhostCache {
 /**
  * When using ghost cache, we assume in_use list is always empty.
  */
-inline void GhostCache::access_impl(uint32_t block_id, uint32_t hash) {
+inline void GhostCache::access_impl(uint32_t block_id, uint32_t hash,
+                                    AccessMode mode) {
   uint32_t size_idx;
   Handle_t s;  // successor
   Handle_t h = cache.refresh(block_id, hash, s);
@@ -210,11 +221,24 @@ inline void GhostCache::access_impl(uint32_t block_id, uint32_t hash) {
     b->value++;
     b = b->next;
   }
-  if (s) {
-    for (uint32_t i = 0; i < size_idx; ++i) caches_stat[i].add_miss();
-    for (uint32_t i = size_idx; i < num_ticks; ++i) caches_stat[i].add_hit();
-  } else {
-    for (uint32_t i = 0; i < num_ticks; ++i) caches_stat[i].add_miss();
+  switch (mode) {
+    case AccessMode::DEFAULT:
+      if (s) {
+        for (uint32_t i = 0; i < size_idx; ++i) caches_stat[i].add_miss();
+        for (uint32_t i = size_idx; i < num_ticks; ++i)
+          caches_stat[i].add_hit();
+      } else {
+        for (uint32_t i = 0; i < num_ticks; ++i) caches_stat[i].add_miss();
+      }
+      break;
+    case AccessMode::AS_MISS:
+      for (uint32_t i = 0; i < num_ticks; ++i) caches_stat[i].add_miss();
+      break;
+    case AccessMode::AS_HIT:
+      for (uint32_t i = 0; i < num_ticks; ++i) caches_stat[i].add_hit();
+      break;
+    case AccessMode::NOOP:
+      break;
   }
 
   *h = 0;

diff --git a/tests/test_ghost.cpp b/tests/test_ghost.cpp
@@ -24,21 +24,38 @@ void test1() {
   ghost_cache.access(1);
   ghost_cache.access(2);
   ghost_cache.access(3);
-  std::cout
-      << "Expect: Boundaries: [1, 0, (null), (null)]; Stat: [0/4, 0/4, 0/4]\n";
+  std::cout << "Expect: Boundaries: [1, 0, (null), (null)]; "
+               "Stat: [0/4, 0/4, 0/4, 0/4]\n";
   std::cout << ghost_cache;
 
   ghost_cache.access(4);
   ghost_cache.access(5);
-  std::cout << "Expect: Boundaries: [3, 2, 1, 0]; Stat: [0/6, 0/6, 0/6]\n";
+  std::cout << "Expect: Boundaries: [3, 2, 1, 0]; Stat: [0/6, 0/6, 0/6, 0/6]\n";
   std::cout << ghost_cache;
 
   ghost_cache.access(2);
-  std::cout << "Expect: Boundaries: [4, 3, 1, 0]; Stat: [0/7, 1/7, 1/7]\n";
+  std::cout << "Expect: Boundaries: [4, 3, 1, 0]; Stat: [0/7, 1/7, 1/7, 1/7]\n";
   std::cout << ghost_cache;
 
   ghost_cache.access(4);
-  std::cout << "Expect: Boundaries: [5, 3, 1, 0]; Stat: [1/8, 2/8, 2/8]\n";
+  std::cout << "Expect: Boundaries: [5, 3, 1, 0]; Stat: [1/8, 2/8, 2/8, 2/8]\n";
+  std::cout << ghost_cache;
+  std::cout << std::flush;
+
+  ghost_cache.access(2, AccessMode::AS_MISS);
+  std::cout << "Expect: Boundaries: [5, 3, 1, 0]; Stat: [1/9, 2/9, 2/9, 2/9]\n";
+  std::cout << ghost_cache;
+  std::cout << std::flush;
+
+  ghost_cache.access(0, AccessMode::AS_HIT);
+  std::cout
+      << "Expect: Boundaries: [4, 5, 3, 1]; Stat: [2/10, 3/10, 3/10, 3/10]\n";
+  std::cout << ghost_cache;
+  std::cout << std::flush;
+
+  ghost_cache.access(7, AccessMode::NOOP);
+  std::cout
+      << "Expect: Boundaries: [2, 4, 5, 3]; Stat: [2/10, 3/10, 3/10, 3/10]\n";
   std::cout << ghost_cache;
   std::cout << std::flush;
 }
@@ -72,6 +89,21 @@ void test2() {
   std::cout << "Expect: Boundaries: [1, 6, 3]; Stat: [0/10, 0/10, 1/10]\n";
   std::cout << ghost_cache;
   std::cout << std::flush;
+
+  ghost_cache.access(8, AccessMode::NOOP);
+  std::cout << "Expect: Boundaries: [4, 7, 5]; Stat: [0/10, 0/10, 1/10]\n";
+  std::cout << ghost_cache;
+  std::cout << std::flush;
+
+  ghost_cache.access(9, AccessMode::AS_HIT);
+  std::cout << "Expect: Boundaries: [8, 1, 6]; Stat: [1/11, 1/11, 2/11]\n";
+  std::cout << ghost_cache;
+  std::cout << std::flush;
+
+  ghost_cache.access(1, AccessMode::AS_MISS);
+  std::cout << "Expect: Boundaries: [9, 4, 6]; Stat: [1/12, 1/12, 2/12]\n";
+  std::cout << ghost_cache;
+  std::cout << std::flush;
 }
 
 void bench1() {