diff --git a/netwerk/cache2/CacheIndex.cpp b/netwerk/cache2/CacheIndex.cpp
index e88b9a1d3..977e3785f 100644
--- a/netwerk/cache2/CacheIndex.cpp
+++ b/netwerk/cache2/CacheIndex.cpp
@@ -69,6 +69,7 @@ public:
   CacheIndexEntryAutoManage(const SHA1Sum::Hash *aHash, CacheIndex *aIndex)
     : mIndex(aIndex)
     , mOldRecord(nullptr)
+    , mOldFrecency(0)
     , mDoNotSearchInIndex(false)
     , mDoNotSearchInUpdates(false)
   {
@@ -79,6 +80,7 @@ public:
     mIndex->mIndexStats.BeforeChange(entry);
     if (entry && entry->IsInitialized() && !entry->IsRemoved()) {
       mOldRecord = entry->mRec;
+      mOldFrecency = entry->mRec->mFrecency;
     }
   }
 
@@ -104,6 +106,8 @@ public:
         mIndex->ReplaceRecordInIterators(mOldRecord, entry->mRec);
         mIndex->RemoveRecordFromFrecencyArray(mOldRecord);
         mIndex->InsertRecordToFrecencyArray(entry->mRec);
+      } else if (entry->mRec->mFrecency != mOldFrecency) {
+        mIndex->mFrecencyArraySorted = false;
       }
     } else {
       // both entries were removed or not initialized, do nothing
@@ -147,6 +151,7 @@ private:
   const SHA1Sum::Hash *mHash;
   RefPtr<CacheIndex> mIndex;
   CacheIndexRecord    *mOldRecord;
+  uint32_t             mOldFrecency;
   bool                 mDoNotSearchInIndex;
   bool                 mDoNotSearchInUpdates;
 };
@@ -246,6 +251,7 @@ CacheIndex::CacheIndex()
   , mRWBufSize(0)
   , mRWBufPos(0)
   , mJournalReadSuccessfully(false)
+  , mFrecencyArraySorted(false)
 {
   sLock.AssertCurrentThreadOwns();
   LOG(("CacheIndex::CacheIndex [this=%p]", this));
@@ -1187,7 +1193,11 @@ CacheIndex::GetEntryForEviction(bool aIgnoreEmptyEntries, SHA1Sum::Hash *aHash,
   uint32_t i;
 
   // find first non-forced valid and unpinned entry with the lowest frecency
-  index->mFrecencyArray.Sort(FrecencyComparator());
+  if (!index->mFrecencyArraySorted) {
+    index->mFrecencyArray.Sort(FrecencyComparator());
+    index->mFrecencyArraySorted = true;
+  }
+
   for (i = 0; i < index->mFrecencyArray.Length(); ++i) {
     memcpy(&hash, &index->mFrecencyArray[i]->mHash, sizeof(SHA1Sum::Hash));
 
@@ -1385,7 +1395,11 @@ CacheIndex::GetIterator(nsILoadContextInfo *aInfo, bool aAddNew,
     iter = new CacheIndexIterator(index, aAddNew);
   }
 
-  index->mFrecencyArray.Sort(FrecencyComparator());
+  if (!index->mFrecencyArraySorted) {
+    index->mFrecencyArray.Sort(FrecencyComparator());
+    index->mFrecencyArraySorted = true;
+  }
+
   iter->AddRecords(index->mFrecencyArray);
 
   index->mIterators.AppendElement(iter);
@@ -3161,6 +3175,7 @@ CacheIndex::InsertRecordToFrecencyArray(CacheIndexRecord *aRecord)
 
   MOZ_ASSERT(!mFrecencyArray.Contains(aRecord));
   mFrecencyArray.AppendElement(aRecord);
+  mFrecencyArraySorted = false;
 }
 
 void
diff --git a/netwerk/cache2/CacheIndex.h b/netwerk/cache2/CacheIndex.h
index 2a6ef9ae7..1a8779761 100644
--- a/netwerk/cache2/CacheIndex.h
+++ b/netwerk/cache2/CacheIndex.h
@@ -1020,6 +1020,7 @@ private:
   // and such entries are stored at the end of the array. Uninitialized entries
   // and entries marked as deleted are not present in this array.
   nsTArray<CacheIndexRecord *>  mFrecencyArray;
+  bool                          mFrecencyArraySorted;
 
   nsTArray<CacheIndexIterator *> mIterators;
 
diff --git a/netwerk/cache2/CacheStorageService.cpp b/netwerk/cache2/CacheStorageService.cpp
index 913bd8aae..24dbd5186 100644
--- a/netwerk/cache2/CacheStorageService.cpp
+++ b/netwerk/cache2/CacheStorageService.cpp
@@ -1239,6 +1239,16 @@ CacheStorageService::PurgeOverMemoryLimit()
 
   LOG(("CacheStorageService::PurgeOverMemoryLimit"));
 
+  static TimeDuration const kFourSeconds = TimeDuration::FromSeconds(4);
+  TimeStamp now = TimeStamp::NowLoRes();
+
+  if (!mLastPurgeTime.IsNull() && now - mLastPurgeTime < kFourSeconds) {
+    LOG(("  bypassed, too soon"));
+    return;
+  }
+
+  mLastPurgeTime = now;
+
   Pool(true).PurgeOverMemoryLimit();
   Pool(false).PurgeOverMemoryLimit();
 }
diff --git a/netwerk/cache2/CacheStorageService.h b/netwerk/cache2/CacheStorageService.h
index c1a6052bf..c699ac799 100644
--- a/netwerk/cache2/CacheStorageService.h
+++ b/netwerk/cache2/CacheStorageService.h
@@ -311,7 +311,7 @@ private:
 
     nsTArray<RefPtr<CacheEntry> > mFrecencyArray;
     nsTArray<RefPtr<CacheEntry> > mExpirationArray;
-    mozilla::Atomic<uint32_t> mMemorySize;
+    Atomic<uint32_t, Relaxed> mMemorySize;
 
     bool OnMemoryConsumptionChange(uint32_t aSavedMemorySize,
                                    uint32_t aCurrentMemoryConsumption);
@@ -330,6 +330,7 @@ private:
 
   MemoryPool mDiskPool;
   MemoryPool mMemoryPool;
+  TimeStamp mLastPurgeTime;
   MemoryPool& Pool(bool aUsingDisk)
   {
     return aUsingDisk ? mDiskPool : mMemoryPool;