SimpleCache: disable size heuristic for code cache eviction

Experiment showed not using the heuristic prevents accumulating too many
files and performs well

Bug: 1075545, 1073514
Change-Id: I7cb374e7f3283ea809f1bf7635f1ade91009742b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2255651Reviewed-by: Mythri Alle <mythria@chromium.org>
Commit-Queue: Maksim Orlovich <morlovich@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781309}

net/disk_cache/simple/simple_index.cc

@@ -58,11 +58,6 @@ static const int kEstimatedEntryOverhead = 512;
 
 namespace disk_cache {
 
-const base::Feature
-    SimpleIndex::kSimpleCacheDisableEvictionSizeHeuristicForCodeCache{
-        "SimpleCacheDisableEvictionSizeHeuristicForCodeCache",
-        base::FEATURE_DISABLED_BY_DEFAULT};
-
 EntryMetadata::EntryMetadata()
     : last_used_time_seconds_since_epoch_(0),
       entry_size_256b_chunks_(0),
@@ -422,11 +417,7 @@ void SimpleIndex::StartEvictionIfNeeded() {
       MEMORY_KB, "Eviction.MaxCacheSizeOnStart2", cache_type_,
       static_cast<base::HistogramBase::Sample>(max_size_ / kBytesInKb));
 
-  bool use_size_heuristic = true;
-  if (cache_type_ == net::GENERATED_BYTE_CODE_CACHE) {
-    use_size_heuristic = !base::FeatureList::IsEnabled(
-        kSimpleCacheDisableEvictionSizeHeuristicForCodeCache);
-  }
+  bool use_size_heuristic = (cache_type_ != net::GENERATED_BYTE_CODE_CACHE);
 
   // Flatten for sorting.
   std::vector<std::pair<uint64_t, const EntrySet::value_type*>> entries;

net/disk_cache/simple/simple_index.h

@@ -14,7 +14,6 @@
 #include <vector>
 
 #include "base/callback.h"
-#include "base/feature_list.h"
 #include "base/files/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
@@ -312,9 +311,6 @@ class NET_EXPORT_PRIVATE SimpleIndex
   // background we can write the index much more frequently, to insure fresh
   // index on next startup.
   bool app_on_background_ = false;
-
-  static const base::Feature
-      kSimpleCacheDisableEvictionSizeHeuristicForCodeCache;
 };
 
 }  // namespace disk_cache

net/disk_cache/simple/simple_index_unittest.cc

@@ -642,10 +642,6 @@ TEST_F(SimpleIndexTest, EvictBySize) {
 }
 
 TEST_F(SimpleIndexCodeCacheTest, DisableEvictBySize) {
-  base::test::ScopedFeatureList scoped_feature_list;
-  scoped_feature_list.InitWithFeatures(
-      {SimpleIndex::kSimpleCacheDisableEvictionSizeHeuristicForCodeCache}, {});
-
   base::Time now(base::Time::Now());
   index()->SetMaxSize(50000);
   InsertIntoIndexFileReturn(hashes_.at<1>(), now - base::TimeDelta::FromDays(2),
@@ -675,40 +671,6 @@ TEST_F(SimpleIndexCodeCacheTest, DisableEvictBySize) {
   ASSERT_EQ(2u, last_doom_entry_hashes().size());
 }
 
-TEST_F(SimpleIndexCodeCacheTest, EnableEvictBySize) {
-  base::test::ScopedFeatureList scoped_feature_list;
-  scoped_feature_list.InitWithFeatures(
-      {}, {SimpleIndex::kSimpleCacheDisableEvictionSizeHeuristicForCodeCache});
-
-  base::Time now(base::Time::Now());
-  index()->SetMaxSize(50000);
-  InsertIntoIndexFileReturn(hashes_.at<1>(), now - base::TimeDelta::FromDays(2),
-                            475u);
-  InsertIntoIndexFileReturn(hashes_.at<2>(), now - base::TimeDelta::FromDays(1),
-                            40000u);
-  ReturnIndexFile();
-  WaitForTimeChange();
-
-  index()->Insert(hashes_.at<3>());
-  // Confirm index is as expected: No eviction, everything there.
-  EXPECT_EQ(3, index()->GetEntryCount());
-  EXPECT_EQ(0, doom_entries_calls());
-  EXPECT_TRUE(index()->Has(hashes_.at<1>()));
-  EXPECT_TRUE(index()->Has(hashes_.at<2>()));
-  EXPECT_TRUE(index()->Has(hashes_.at<3>()));
-
-  // Trigger an eviction, and make sure the right things are tossed.
-  // This has size-weighting enabled, so it end sup kickicking out entry
-  // 2, which is biggest, and is enough, even though <1> is older.
-  index()->UpdateEntrySize(hashes_.at<3>(), 40000u);
-  EXPECT_EQ(1, doom_entries_calls());
-  EXPECT_EQ(2, index()->GetEntryCount());
-  EXPECT_TRUE(index()->Has(hashes_.at<1>()));
-  EXPECT_FALSE(index()->Has(hashes_.at<2>()));
-  EXPECT_TRUE(index()->Has(hashes_.at<3>()));
-  ASSERT_EQ(1u, last_doom_entry_hashes().size());
-}
-
 // Same as test above, but using much older entries to make sure that small
 // things eventually get evictied.
 TEST_F(SimpleIndexTest, EvictBySize2) {