evict larger entries first

net/disk_cache/simple/simple_experiment.cc

Index: net/disk_cache/simple/simple_experiment.cc
diff --git a/net/disk_cache/simple/simple_experiment.cc b/net/disk_cache/simple/simple_experiment.cc
index 38ea589322f97df405f9b48bcaa349510847ce52..dc7b6cd0ae7a0c92e543cc8ceccf7b0179c33a83 100644
--- a/net/disk_cache/simple/simple_experiment.cc
+++ b/net/disk_cache/simple/simple_experiment.cc
@@ -15,10 +15,44 @@ namespace disk_cache {
 
 const base::Feature kSimpleSizeExperiment = {"SimpleSizeExperiment",
                                              base::FEATURE_DISABLED_BY_DEFAULT};
+const base::Feature kSimpleCacheEvictionWithSizeExperiment = {
+    "SimpleCacheEvictionWithSizeExperiment", base::FEATURE_DISABLED_BY_DEFAULT};
+
 const char kSizeMultiplierParam[] = "SizeMultiplier";
+const char kSizeEvictionParam[] = "SizeEviction";
 
 namespace {
 
+// Updates experiment if the experiment is active.
+bool CheckForEvictionWithSizeExperiment(
+    disk_cache::SimpleExperiment* experiment) {
+  if (disk_cache::SimpleExperimentType::NONE != experiment->type)

[jkarlin, 2017/07/12 15:51:40]

After returning early in GetSimpleExperiment you can turn this into a DCHECK

[hubbe, 2017/07/12 18:22:50]

Done.

+    return false;
+
+  if (!base::FeatureList::IsEnabled(kSimpleCacheEvictionWithSizeExperiment))
+    return false;
+
+  base::FieldTrial* trial =
+      base::FeatureList::GetFieldTrial(kSimpleCacheEvictionWithSizeExperiment);
+  if (!trial)
+    return false;
+
+  std::map<std::string, std::string> params;
+  base::FieldTrialParamAssociator::GetInstance()->GetFieldTrialParams(
+      trial->trial_name(), &params);
+  auto iter = params.find(kSizeEvictionParam);
+  if (iter == params.end())
+    return false;
+
+  uint32_t param;
+  if (!base::StringToUint(iter->second, &param))
+    return false;
+
+  experiment->type = disk_cache::SimpleExperimentType::SIZE;

[jkarlin, 2017/07/12 15:51:41]

I believe you want EVICT_WITH_SIZE here ;) That would have been caught with a
unittest. Please add relevant tests to simple_experiment_unittest.cc

[hubbe, 2017/07/12 18:22:50]

Done.

+  experiment->param = param;
+  return true;
+}
+
 // Returns true if the experiment is found and properly defined.
 bool CheckForSimpleSizeExperiment(disk_cache::SimpleExperiment* experiment) {
   DCHECK_EQ(disk_cache::SimpleExperimentType::NONE, experiment->type);
@@ -58,6 +92,7 @@ SimpleExperiment GetSimpleExperiment(net::CacheType cache_type) {
     return experiment;
 
   CheckForSimpleSizeExperiment(&experiment);

[jkarlin, 2017/07/12 15:51:41]

Can you have each check return early if they return true to give us clear
semantics that the first matching experiment wins.

[hubbe, 2017/07/12 18:22:50]

Done.

+  CheckForEvictionWithSizeExperiment(&experiment);
   return experiment;
 }