Fix performance regression in OatFile::GetOatDexFile().
Try to avoid calculating the canonical location of the
dex file if possible and when we have to calculate it,
cache the lookup result for subsequent lookups.
Bug: 16828525
Bug: 16859671
Change-Id: I0f03007ba5adf08656615900cf125075a3f2c541
diff --git a/runtime/oat_file.h b/runtime/oat_file.h
index 3ec2e84..9710a2a 100644
--- a/runtime/oat_file.h
+++ b/runtime/oat_file.h
@@ -17,9 +17,11 @@
#ifndef ART_RUNTIME_OAT_FILE_H_
#define ART_RUNTIME_OAT_FILE_H_
+#include <list>
#include <string>
#include <vector>
+#include "base/mutex.h"
#include "base/stringpiece.h"
#include "dex_file.h"
#include "invoke_type.h"
@@ -227,7 +229,8 @@
const OatDexFile* GetOatDexFile(const char* dex_location,
const uint32_t* const dex_location_checksum,
- bool exception_if_not_found = true) const;
+ bool exception_if_not_found = true) const
+ LOCKS_EXCLUDED(secondary_lookup_lock_);
std::vector<const OatDexFile*> GetOatDexFiles() const;
@@ -279,10 +282,38 @@
// dlopen handle during runtime.
void* dlopen_handle_;
- // NOTE: We use a StringPiece as the key type to avoid a memory allocation on every lookup
- // with a const char* key.
+ // NOTE: We use a StringPiece as the key type to avoid a memory allocation on every
+ // lookup with a const char* key. The StringPiece doesn't own its backing storage,
+ // therefore we're using the OatDexFile::dex_file_location_ as the backing storage
+ // for keys in oat_dex_files_ and the string_cache_ entries for the backing storage
+ // of keys in secondary_oat_dex_files_ and oat_dex_files_by_canonical_location_.
typedef SafeMap<StringPiece, const OatDexFile*> Table;
- Table oat_dex_files_;
+
+ // Map each plain dex file location retrieved from the oat file to its OatDexFile.
+ // This map doesn't change after it's constructed in Setup() and therefore doesn't
+ // need any locking and provides the cheapest dex file lookup for GetOatDexFile()
+ // for a very frequent use case. Never contains a nullptr value.
+ Table oat_dex_files_; // Owns the OatDexFile* values.
+
+ // Lock guarding all members needed for secondary lookup in GetOatDexFile().
+ mutable Mutex secondary_lookup_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
+
+ // If the primary oat_dex_files_ lookup fails, use a secondary map. This map stores
+ // the results of all previous secondary lookups, whether successful (non-null) or
+ // failed (null). If it doesn't contain an entry we need to calculate the canonical
+ // location and use oat_dex_files_by_canonical_location_.
+ mutable Table secondary_oat_dex_files_ GUARDED_BY(secondary_lookup_lock_);
+
+ // Map the canonical location to an OatDexFile. This lazily constructed map is used
+ // when we're doing the secondary lookup for a given location for the first time.
+ mutable Table oat_dex_files_by_canonical_location_ GUARDED_BY(secondary_lookup_lock_);
+
+ // Cache of strings. Contains the backing storage for keys in the secondary_oat_dex_files_
+ // and the lazily initialized oat_dex_files_by_canonical_location_.
+ // NOTE: We're keeping references to contained strings in form of StringPiece and adding
+ // new strings to the end. The adding of a new element must not touch any previously stored
+ // elements. std::list<> and std::deque<> satisfy this requirement, std::vector<> doesn't.
+ mutable std::list<std::string> string_cache_ GUARDED_BY(secondary_lookup_lock_);
friend class OatClass;
friend class OatDexFile;