SimpleCache: read small files all at once.

net/disk_cache/disk_cache_test_base.cc

Index: net/disk_cache/disk_cache_test_base.cc
diff --git a/net/disk_cache/disk_cache_test_base.cc b/net/disk_cache/disk_cache_test_base.cc
index 0776572622edd66caffce95efebce91f55bcfbe0..9b6b0edb01e0034c7a2dab669f3505809c85d343 100644
--- a/net/disk_cache/disk_cache_test_base.cc
+++ b/net/disk_cache/disk_cache_test_base.cc
@@ -8,9 +8,13 @@
 
 #include "base/files/file_util.h"
 #include "base/message_loop/message_loop.h"
+#include "base/metrics/field_trial.h"
+#include "base/metrics/field_trial_param_associator.h"
 #include "base/path_service.h"
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
+#include "base/test/mock_entropy_provider.h"
+#include "base/test/scoped_feature_list.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "net/base/io_buffer.h"
@@ -22,6 +26,7 @@
 #include "net/disk_cache/disk_cache_test_util.h"
 #include "net/disk_cache/memory/mem_backend_impl.h"
 #include "net/disk_cache/simple/simple_backend_impl.h"
+#include "net/disk_cache/simple/simple_experiment.h"
 #include "net/disk_cache/simple/simple_index.h"
 #include "net/test/gtest_util.h"
 #include "testing/gmock/include/gmock/gmock.h"
@@ -87,6 +92,21 @@ DiskCacheTestWithCache::DiskCacheTestWithCache()
       integrity_(true),
       use_current_thread_(false),
       cache_thread_("CacheThread") {
+  // Make sure to cover the prefetch path in SimpleCache.

[pasko, 2017/07/18 14:02:56]

doing work in constructors is generally discouraged...


The bigger issue is that we need a test to experiment with different params,
while most of the tests should run with param 0. There is a standard mechanism
to get coverage for different values of params as we roll to channels, there is
a json file to override the base::Feature for testing and set the most popular
configuration there. When submitting the Finch config you'll likely get a
warning about that. So that'd be preferable IMO.

[morlovich, 2017/07/18 14:32:31]

Any keyword to search for/pointer for that mechanism?

[pasko, 2017/07/19 16:28:26]

go/finch101 and search for "testing-config", but  you'll need to read the whole
page anyway, which makes searching unnecessary

[Maks Orlovich, 2017/07/25 16:06:29]

Removed this from here (and added for the dedicated test)

+  field_trial_list_ = base::MakeUnique<base::FieldTrialList>(
+      base::MakeUnique<base::MockEntropyProvider>());
+  scoped_refptr<base::FieldTrial> trial =
+      base::FieldTrialList::CreateFieldTrial("UnitTest", "Group");
+  std::map<std::string, std::string> params;
+  params[disk_cache::kSimplePrefetchBytesParam] = "32768";
+  base::FieldTrialParamAssociator::GetInstance()->AssociateFieldTrialParams(
+      "UnitTest", "Group", params);
+
+  std::unique_ptr<base::FeatureList> feature_list(new base::FeatureList);
+  feature_list->RegisterFieldTrialOverride(
+      disk_cache::kSimpleCachePrefetchExperiment.name,
+      base::FeatureList::OVERRIDE_ENABLE_FEATURE, trial.get());
+  scoped_feature_list_.InitWithFeatureList(std::move(feature_list));
 }
 
 DiskCacheTestWithCache::~DiskCacheTestWithCache() {}