Bug 1662011 - Remove hash stats code from the cache, r=valentin,necko-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D88739

netwerk/cache2/CacheIndex.cpp

@@ -3274,11 +3274,6 @@ void CacheIndex::ChangeState(EState aNewState) {
     return;
   }
 
-  if ((mState == READING || mState == BUILDING || mState == UPDATING) &&
-      aNewState == READY) {
-    ReportHashStats();
-  }
-
   // Try to evict entries over limit everytime we're leaving state READING,
   // BUILDING or UPDATING, but not during shutdown or when removing all
   // entries.
@@ -3807,73 +3802,6 @@ size_t CacheIndex::SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) {
   return mallocSizeOf(gInstance) + SizeOfExcludingThis(mallocSizeOf);
 }
 
-namespace {
-
-class HashComparator {
- public:
-  bool Equals(CacheIndexRecord* a, CacheIndexRecord* b) const {
-    return memcmp(&a->mHash, &b->mHash, sizeof(SHA1Sum::Hash)) == 0;
-  }
-  bool LessThan(CacheIndexRecord* a, CacheIndexRecord* b) const {
-    return memcmp(&a->mHash, &b->mHash, sizeof(SHA1Sum::Hash)) < 0;
-  }
-};
-
-void ReportHashSizeMatch(const SHA1Sum::Hash* aHash1,
-                         const SHA1Sum::Hash* aHash2) {
-  const uint32_t* h1 = reinterpret_cast<const uint32_t*>(aHash1);
-  const uint32_t* h2 = reinterpret_cast<const uint32_t*>(aHash2);
-
-  for (uint32_t i = 0; i < 5; ++i) {
-    if (h1[i] != h2[i]) {
-      uint32_t bitsDiff = h1[i] ^ h2[i];
-      bitsDiff = NetworkEndian::readUint32(&bitsDiff);
-
-      // count leading zeros in bitsDiff
-      static const uint8_t debruijn32[32] = {
-          0, 31, 9, 30, 3, 8,  13, 29, 2,  5,  7,  21, 12, 24, 28, 19,
-          1, 10, 4, 14, 6, 22, 25, 20, 11, 15, 23, 26, 16, 27, 17, 18};
-
-      bitsDiff |= bitsDiff >> 1;
-      bitsDiff |= bitsDiff >> 2;
-      bitsDiff |= bitsDiff >> 4;
-      bitsDiff |= bitsDiff >> 8;
-      bitsDiff |= bitsDiff >> 16;
-      bitsDiff++;
-
-      uint8_t hashSizeMatch =
-          debruijn32[bitsDiff * 0x076be629 >> 27] + (i << 5);
-      Telemetry::Accumulate(Telemetry::NETWORK_CACHE_HASH_STATS, hashSizeMatch);
-
-      return;
-    }
-  }
-
-  MOZ_ASSERT(false, "Found a collision in the index!");
-}
-
-}  // namespace
-
-void CacheIndex::ReportHashStats() {
-  // We're gathering the hash stats only once, exclude too small caches.
-  if (CacheObserver::HashStatsReported() || mFrecencyArray.Length() < 15000) {
-    return;
-  }
-
-  nsTArray<CacheIndexRecord*> records;
-  for (auto iter = mFrecencyArray.Iter(); !iter.Done(); iter.Next()) {
-    records.AppendElement(iter.Get());
-  }
-
-  records.Sort(HashComparator());
-
-  for (uint32_t i = 1; i < records.Length(); i++) {
-    ReportHashSizeMatch(&records[i - 1]->mHash, &records[i]->mHash);
-  }
-
-  CacheObserver::SetHashStatsReported();
-}
-
 // static
 void CacheIndex::UpdateTotalBytesWritten(uint32_t aBytesWritten) {
   StaticMutexAutoLock lock(sLock);

netwerk/cache2/CacheIndex.h

@@ -1040,8 +1040,6 @@ class CacheIndex final : public CacheFileIOListener, public nsIRunnable {
   // Memory reporting (private part)
   size_t SizeOfExcludingThisInternal(mozilla::MallocSizeOf mallocSizeOf) const;
 
-  void ReportHashStats();
-
   // Reports telemetry about cache, i.e. size, entry count and content type
   // stats.
   void DoTelemetryReport();

netwerk/cache2/CacheObserver.cpp

@@ -38,9 +38,6 @@ Atomic<uint32_t, Relaxed> CacheObserver::sSmartDiskCacheCapacity(1024 * 1024);
 static bool kDefaultCacheFSReported = false;
 bool CacheObserver::sCacheFSReported = kDefaultCacheFSReported;
 
-static bool kDefaultHashStatsReported = false;
-bool CacheObserver::sHashStatsReported = kDefaultHashStatsReported;
-
 Atomic<PRIntervalTime> CacheObserver::sShutdownDemandedTime(
     PR_INTERVAL_NO_TIMEOUT);
 
@@ -163,29 +160,6 @@ void CacheObserver::StoreCacheFSReported() {
                                sCacheFSReported);
 }
 
-// static
-void CacheObserver::SetHashStatsReported() {
-  sHashStatsReported = true;
-
-  if (!sSelf) {
-    return;
-  }
-
-  if (NS_IsMainThread()) {
-    sSelf->StoreHashStatsReported();
-  } else {
-    nsCOMPtr<nsIRunnable> event =
-        NewRunnableMethod("net::CacheObserver::StoreHashStatsReported",
-                          sSelf.get(), &CacheObserver::StoreHashStatsReported);
-    NS_DispatchToMainThread(event);
-  }
-}
-
-void CacheObserver::StoreHashStatsReported() {
-  mozilla::Preferences::SetInt("browser.cache.disk.hashstats_reported",
-                               sHashStatsReported);
-}
-
 // static
 void CacheObserver::ParentDirOverride(nsIFile** aDir) {
   if (NS_WARN_IF(!aDir)) return;

netwerk/cache2/CacheObserver.h

@@ -77,8 +77,6 @@ class CacheObserver : public nsIObserver, public nsSupportsWeakReference {
   }
   static bool CacheFSReported() { return sCacheFSReported; }
   static void SetCacheFSReported();
-  static bool HashStatsReported() { return sHashStatsReported; }
-  static void SetHashStatsReported();
   static void ParentDirOverride(nsIFile** aDir);
 
   static bool EntryIsTooBig(int64_t aSize, bool aUsingDisk);
@@ -96,14 +94,12 @@ class CacheObserver : public nsIObserver, public nsSupportsWeakReference {
   static StaticRefPtr<CacheObserver> sSelf;
 
   void StoreCacheFSReported();
-  void StoreHashStatsReported();
   void AttachToPreferences();
 
   static int32_t sAutoMemoryCacheCapacity;
   static Atomic<uint32_t, Relaxed> sSmartDiskCacheCapacity;
   static float sHalfLifeHours;
   static bool sCacheFSReported;
-  static bool sHashStatsReported;
   static Atomic<PRIntervalTime> sShutdownDemandedTime;
 
   // Non static properties, accessible via sSelf

toolkit/components/telemetry/Histograms.json

@@ -11338,14 +11338,6 @@
     "n_buckets": 66,
     "description": "Size of the metadata in bytes parsed from the disk."
   },
-  "NETWORK_CACHE_HASH_STATS": {
-    "record_in_processes": ["main", "content"],
-    "products": ["firefox", "fennec"],
-    "expires_in_version": "46",
-    "kind": "enumerated",
-    "n_values": 160,
-    "description": "The longest hash match between a newly added entry and all the existing entries."
-  },
   "NETWORK_CACHE_SIZE" : {
     "record_in_processes": ["main"],
     "products": ["firefox", "fennec"],

toolkit/components/telemetry/histogram-allowlists.json

@@ -222,7 +222,6 @@
     "MOZ_SQLITE_WEBAPPS_WRITE_MAIN_THREAD_MS",
     "MOZ_SQLITE_WEBAPPS_WRITE_MS",
     "NETWORK_CACHE_FS_TYPE",
-    "NETWORK_CACHE_HASH_STATS",
     "NETWORK_CACHE_HIT_MISS_STAT_PER_CACHE_SIZE",
     "NETWORK_CACHE_HIT_RATE_PER_CACHE_SIZE",
     "NETWORK_CACHE_METADATA_FIRST_READ_TIME_MS",
@@ -689,7 +688,6 @@
     "MOZ_STORAGE_ASYNC_REQUESTS_MS",
     "MOZ_STORAGE_ASYNC_REQUESTS_SUCCESS",
     "NETWORK_CACHE_FS_TYPE",
-    "NETWORK_CACHE_HASH_STATS",
     "NETWORK_CACHE_HIT_MISS_STAT_PER_CACHE_SIZE",
     "NETWORK_CACHE_HIT_RATE_PER_CACHE_SIZE",
     "NETWORK_CACHE_METADATA_FIRST_READ_TIME_MS",
@@ -1048,7 +1046,6 @@
     "DEVTOOLS_HEAP_SNAPSHOT_NODE_COUNT",
     "DEVTOOLS_HEAP_SNAPSHOT_EDGE_COUNT",
     "NETWORK_CACHE_HIT_RATE_PER_CACHE_SIZE",
-    "NETWORK_CACHE_HASH_STATS",
     "SSL_CIPHER_SUITE_FULL",
     "SSL_CIPHER_SUITE_RESUMED",
     "SSL_HANDSHAKE_RESULT",