Implementation of fast lookup table to search class_def by descriptor
Lookup table is a hash table which built at compile time and stored
into oat file. At runtime the table is restored and used in the
method DexFile::FindClassDef(const char*) to perform fast search of
the class_def_idx by class descriptor. Advantages of the lookup table
over the HashSet (runtime/base/hash_set.h) are:
1. Lookup table is built at compile time and uses read-only memory at
runtime
2. Lookup table uses less memory then DexFile::Index (less by 80% for
/system/framework/framework.jar on Nexus5)
3. Lookup table does less string comparisons compared with HashSet
(less by 70% for zygote process on Nexus5)
The disadvantage of the lookup table is it increased boot.oat size by
0.2% on Nexus5 and application .oat file by 0.3% in average on Nexus5.
mathieuc changes:
Create lookup table in dex2oat to speed up compilation. Clean up code
to follow style guide and use less static functions. Added
performance measurements.
Compile ~100 APKs 5 times with filter interpret-only:
Before:
real 1m8.989s
user 0m59.318s
sys 0m7.773s
After:
real 1m1.493s
user 0m52.055s
sys 0m7.581s
App launch (AOSP N5 maps, average of 45 runs):
Before: 966.84ms
After: 923.733ms
Launch speedup is 4.7%
Memory usage compared to HashSet index on 50 various APK:
32 bit: HashSet ~625694b vs TypeLookupTable ~404268b
64 bit: HashSet ~1251390b vs TypeLookupTable ~404268b
Bug: 10921004
Bug: 20269715
Change-Id: I7246c1d9ad9fe81fe5c5907a4bf70396d8f9242a
diff --git a/runtime/oat_file.h b/runtime/oat_file.h
index 6acdf86..0a77654 100644
--- a/runtime/oat_file.h
+++ b/runtime/oat_file.h
@@ -400,6 +400,10 @@
return dex_cache_arrays_;
}
+ const uint8_t* GetLookupTableData() const {
+ return lookup_table_data_;
+ }
+
~OatDexFile();
private:
@@ -408,6 +412,7 @@
const std::string& canonical_dex_file_location,
uint32_t dex_file_checksum,
const uint8_t* dex_file_pointer,
+ const uint8_t* lookup_table_data,
const uint32_t* oat_class_offsets_pointer,
uint8_t* dex_cache_arrays);
@@ -416,6 +421,7 @@
const std::string canonical_dex_file_location_;
const uint32_t dex_file_location_checksum_;
const uint8_t* const dex_file_pointer_;
+ const uint8_t* lookup_table_data_;
const uint32_t* const oat_class_offsets_pointer_;
uint8_t* const dex_cache_arrays_;