RFC: use some in-memory state in SimpleCache to quickly cache-miss some CantConditionalize cases

net/disk_cache/simple/simple_index.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/disk_cache/simple/simple_index.h"
 
 #include <algorithm>
 #include <limits>
 #include <string>
 #include <utility>
@@ skipping 42 matching lines @@
 
 namespace disk_cache {
 
 EntryMetadata::EntryMetadata()
   : last_used_time_seconds_since_epoch_(0),
     entry_size_(0) {
 }
 
 EntryMetadata::EntryMetadata(base::Time last_used_time,
                              base::StrictNumeric<uint32_t> entry_size)
-    : last_used_time_seconds_since_epoch_(0), entry_size_(entry_size) {
+    : last_used_time_seconds_since_epoch_(0), entry_size_(0) {
+  SetEntrySize(entry_size);  // to round/pack properly.
   SetLastUsedTime(last_used_time);
 }
 
 base::Time EntryMetadata::GetLastUsedTime() const {
   // Preserve nullity.
   if (last_used_time_seconds_since_epoch_ == 0)
     return base::Time();
 
   return base::Time::UnixEpoch() +
       base::TimeDelta::FromSeconds(last_used_time_seconds_since_epoch_);
 }
 
 void EntryMetadata::SetLastUsedTime(const base::Time& last_used_time) {
   // Preserve nullity.
   if (last_used_time.is_null()) {
     last_used_time_seconds_since_epoch_ = 0;
     return;
   }
 
   last_used_time_seconds_since_epoch_ = base::saturated_cast<uint32_t>(
       (last_used_time - base::Time::UnixEpoch()).InSeconds());
   // Avoid accidental nullity.
   if (last_used_time_seconds_since_epoch_ == 0)
     last_used_time_seconds_since_epoch_ = 1;
 }
 
 uint32_t EntryMetadata::GetEntrySize() const {
-  return entry_size_;
+  return entry_size_ << 8;
 }
 
 void EntryMetadata::SetEntrySize(base::StrictNumeric<uint32_t> entry_size) {
-  entry_size_ = entry_size;
+  // ### what happens if we overflow here?
+  entry_size_ = (static_cast<uint32_t>(entry_size) + 255) >> 8;
 }
 
 void EntryMetadata::Serialize(base::Pickle* pickle) const {
   DCHECK(pickle);
   int64_t internal_last_used_time = GetLastUsedTime().ToInternalValue();
   // If you modify the size of the size of the pickle, be sure to update
   // kOnDiskSizeBytes.
   pickle->WriteInt64(internal_last_used_time);
   pickle->WriteUInt64(entry_size_);
 }
 
-bool EntryMetadata::Deserialize(base::PickleIterator* it) {
+bool EntryMetadata::Deserialize(base::PickleIterator* it,
+                                bool has_memory_entry_data) {
   DCHECK(it);
   int64_t tmp_last_used_time;
   uint64_t tmp_entry_size;
   if (!it->ReadInt64(&tmp_last_used_time) || !it->ReadUInt64(&tmp_entry_size) ||
       tmp_entry_size > std::numeric_limits<decltype(entry_size_)>::max())
     return false;
   SetLastUsedTime(base::Time::FromInternalValue(tmp_last_used_time));
-  entry_size_ = static_cast<uint32_t>(tmp_entry_size);
+  if (has_memory_entry_data) {
+    // tmp_entry_size actually packs entry_size_ and memory_entry_data_.
+    SetEntrySize(static_cast<uint32_t>(tmp_entry_size & 0xFFFFFF00));
+    SetMemoryEntryData(static_cast<uint8_t>(tmp_entry_size & 0xFF));
+  } else {
+    SetEntrySize(static_cast<uint32_t>(tmp_entry_size));
+    SetMemoryEntryData(0);
+  }
   return true;
 }
 
 SimpleIndex::SimpleIndex(
     const scoped_refptr<base::SingleThreadTaskRunner>& io_thread,
     SimpleIndexDelegate* delegate,
     net::CacheType cache_type,
     std::unique_ptr<SimpleIndexFile> index_file)
     : delegate_(delegate),
       cache_type_(cache_type),
@@ skipping 148 matching lines @@
     removed_entries_.insert(entry_hash);
   PostponeWritingToDisk();
 }
 
 bool SimpleIndex::Has(uint64_t hash) const {
   DCHECK(io_thread_checker_.CalledOnValidThread());
   // If not initialized, always return true, forcing it to go to the disk.
   return !initialized_ || entries_set_.count(hash) > 0;
 }
 
+uint8_t SimpleIndex::GetMemoryEntryData(uint64_t entry_hash) const {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
+  EntrySet::const_iterator it = entries_set_.find(entry_hash);
+  if (it == entries_set_.end())
+    return 0;
+  return it->second.GetMemoryEntryData();
+}
+
+void SimpleIndex::SetMemoryEntryData(uint64_t entry_hash, uint8_t value) {
+  DCHECK(io_thread_checker_.CalledOnValidThread());
+  EntrySet::iterator it = entries_set_.find(entry_hash);
+  if (it == entries_set_.end())
+    return;
+  return it->second.SetMemoryEntryData(value);
+}
+
 bool SimpleIndex::UseIfExists(uint64_t entry_hash) {
   DCHECK(io_thread_checker_.CalledOnValidThread());
   // Always update the last used time, even if it is during initialization.
   // It will be merged later.
   EntrySet::iterator it = entries_set_.find(entry_hash);
   if (it == entries_set_.end())
     // If not initialized, always return true, forcing it to go to the disk.
     return !initialized_;
   it->second.SetLastUsedTime(base::Time::Now());
   PostponeWritingToDisk();
@@ skipping 109 matching lines @@
       FROM_HERE, base::TimeDelta::FromMilliseconds(delay), write_to_disk_cb_);
 }
 
 void SimpleIndex::UpdateEntryIteratorSize(
     EntrySet::iterator* it,
     base::StrictNumeric<uint32_t> entry_size) {
   // Update the total cache size with the new entry size.
   DCHECK(io_thread_checker_.CalledOnValidThread());
   DCHECK_GE(cache_size_, (*it)->second.GetEntrySize());
   cache_size_ -= (*it)->second.GetEntrySize();
-  cache_size_ += static_cast<uint32_t>(entry_size);
   (*it)->second.SetEntrySize(entry_size);
+  // We use GetEntrySize to get consistent rounding.
+  cache_size_ += (*it)->second.GetEntrySize();
 }
 
 void SimpleIndex::MergeInitializingSet(
     std::unique_ptr<SimpleIndexLoadResult> load_result) {
   DCHECK(io_thread_checker_.CalledOnValidThread());
   DCHECK(load_result->did_load);
 
   EntrySet* index_file_entries = &load_result->entries;
 
   for (std::unordered_set<uint64_t>::const_iterator it =
@@ skipping 89 matching lines @@
                        start - last_write_to_disk_);
     }
   }
   last_write_to_disk_ = start;
 
   index_file_->WriteToDisk(reason, entries_set_, cache_size_, start,
                            app_on_background_, base::Closure());
 }
 
 }  // namespace disk_cache