Method and apparatus for loading classes and re-organizing class archives

• US 9,477,496 B2
• Filed: 02/26/2009
• Issued: 10/25/2016
• Est. Priority Date: 02/27/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Chi, Chang Yan, Li, Xin Hui, Xiao, Wen Peng
• Primary Examiner(s): Zhen, Wei
• Assistant Examiner(s): HUDA, MOHAMMED NURUL
• Application Number:
  US12/393,302
• Publication Number:
  US 20090217022A1
• Time in Patent Office: 2,798 Days
• Field of Search: 717/166
• US Class Current: 1/1
• CPC Class Codes: G06F 9/44521 Dynamic linking or loading; Link editing at or after load time, e.g. Java class loading

Abstract

A method and apparatus for loading classes to virtual machines and a method and apparatus for reorganizing class archives. The method for loading a class to a virtual machine includes organizing a class archive before class loading such that the organized class archive includes a class contraction portion and loading only the class contraction portion of the class archive to the virtual machine at the moment of class loading. By first loading the class contraction portion from the organized class archive to the virtual machine at the moment of loading, the present invention curtails code redundancy, shortens loading time and reduces occupied memory resources.

Claims

1. A method for loading a class to a virtual machine, comprising:

separating, using a separator module, each of a plurality of classes of a class archive into a skeleton, contents, and an index file having references to the contents associated with the skeleton of each class;

organizing the class archive before class loading such that the organized class archive includes a class contraction portion and a rest portion, wherein the class contraction portion comprises a plurality of skeletons, one skeleton for each class, and the rest portion comprises a plurality of contents, one content for each corresponding skeleton;

verifying a security of the class archive using a security verification module, wherein verification comprises loading and carrying out verification of a plurality of symbolic references except a verification of bytecodes on a loaded skeleton;

loading only the class contraction portion of the class archive to the virtual machine using a load tracker;

wherein the class contraction portion comprises only a basic class information portion of each of the plurality of classes in the class archive and the rest portion comprises a detailed class information portion of each of the plurality of classes that is not included in the class contraction portion, and

wherein the basic class information consists of a magic code, a major version number, a minor version number, a count of constants, a constant pool and access flags and wherein the detailed class information comprises variables, methods and attributes and counts thereof;

executing a program using the class archive at the virtual machine;

loading, during runtime using a load tracker, a plurality of needed contents not loaded prior to executing the program;

recording class usage information at runtime using a run recorder, wherein the class usage information comprises one or more of a miss rate of skeletons or contents, missed skeletons or contents and a non-usage rate of skeletons or contents, the missed skeletons or contents being recorded in a first-in first-out manner using a storage space with a fixed size; and

optimizing the class archive by removing a plurality of unused skeletons during runtime from the class contraction portion of the class archive, and adding a plurality of contents loaded during runtime to the class contraction portion of the class archive.

2. The method according to claim 1, further comprising:

reorganizing the class archive according to the class usage information such that the class archive includes the class contraction portion to be loaded.

3. The method according to claim 2, wherein:

the skeletons or contents are added to the class contraction portion when the miss rate exceeds a predetermined threshold based on the index file of the class;

the skeletons or contents left in the storage space at the end of running are added to the class contraction portion based on the index file of the class; and

the skeletons or contents are removed from the class contraction portion when the non-usage rate exceeds another predetermined threshold based on the index file of the class.

4. The method according to claim 2, further comprising:

recording the loading sequence of the class at the moment of loading; and

sorting the class contraction portion in accordance with the loading sequence such that sorting of the class contraction portion is consistent with the loading sequence.

5. The method according to claim 1, further comprising:

carrying out internal verification during class loading; and

carrying out verification of symbolic references during execution of bytecodes.

6. An apparatus for loading a class into a memory of a virtual machine, comprising:

a class loader having a load tracker configured to record a loading sequence of the class;

a class archive comprising a plurality of classes and each of the plurality of classes having a class contraction portion, a rest portion;

wherein the class archive is organized before class loading such that the organized class archive includes the class contraction portion of the class archive;

wherein the class loader is configured to load only the class contraction portion of the class archive to the virtual machine;

a separator module configured to separate each of the plurality of classes of the class archive into a skeleton, contents, and an index file, wherein the class contraction portion comprises a plurality of skeletons, one skeleton for each class, the rest portion comprises a plurality of contents, one content for each corresponding skeleton, and the index file comprises references to the rest portion associated with the skeleton portion of each class;

a security verification module configured to verify a security of the class archive, wherein verification comprises loading and carrying out verification of a plurality of symbolic references except a verification of bytecodes on a loaded skeleton;

wherein the class contraction portion comprises only a basic class information portion of each of the plurality of classes in the class archive and the rest portion comprises a detailed class information portion of each of the plurality of classes that is not included in the class contraction portion, wherein the basic class information consists of a magic code, a major version number, a minor version number, a count of constants, a constant pool and access flags and wherein the detailed class information comprises variables, methods and attributes and counts thereof; and

a run recorder configured to record class usage information at runtime, wherein the class usage information comprises one or more of a miss rate of skeletons or contents, missed skeletons or contents and a non-usage rate of skeletons or contents, the missed skeletons or contents being recorded in a first-in first-out manner using a storage space with a fixed size; and

a processor configured to optimize the class archive by removing a plurality of unused skeletons during runtime from the class contraction portion of the class archive, and adding a plurality of contents loaded during runtime to the class contraction portion of the class archive.

7. The apparatus according to claim 6, further comprising:

a reorganizer configured to reorganize the class archive according to the class usage information such that the class archive includes the class contraction portion.

8. The apparatus according to claim 7, wherein:

the reorganizer is configured to reorganize the class archive by;

adding the skeletons or contents to the class contraction portion when the miss rate exceeds a predetermined threshold based on the index file of the class;

adding skeletons or contents left in the storage space at the end of running to the class contraction portion based on the index file of the class;

or

removing the skeletons or contents from the class contraction portion when the non-usage rate exceeds another predetermined threshold based on the index file of the class.

9. The apparatus according to claim 8, wherein the reorganizer is further configured to sort the class contraction portion in accordance with the loading sequence such that the sorting of the class contraction portion is consistent with the loading sequence.

10. The apparatus according to claim 6, further comprising:

a security verifier configured to carry out (i) internal verification during class loading and (ii) verification of symbolic references during execution of bytecodes.

11. A method for reorganizing a class archive comprising a plurality of classes, comprising:

separating, using a separator module, each of the plurality of classes of the class archive into a skeleton, contents, and an index file having references to the contents associated with the skeleton of each class;

organizing the class archive before class loading such that the organized class archive includes a class contraction portion and a rest portion, wherein the class contraction portion comprises a plurality of skeletons, one skeleton for each class and the rest portion comprises a plurality of contents, one content for each corresponding skeleton;

verifying a security of the class archive using a security verification module, wherein verification comprises loading and carrying out verification of a plurality of symbolic references except a verification of bytecodes on a loaded skeleton;

loading only the class contraction portion of the class archive to a virtual machine using a load tracker;

wherein the class contraction portion comprises only a basic class information portion of each of the plurality of classes in the class archive and the rest portion comprises a detailed class information portion of each of the plurality of classes that is not included in the class contraction portion, wherein the basic class information consists of a magic code, a major version number, a minor version number, a count of constants, a constant pool and access flags and wherein the detailed class information comprises variables, methods and attributes and counts thereof;

executing a program using the class archive at the virtual machine;

loading, during runtime using the load tracker, a plurality of needed contents not loaded prior to executing the program;

recording class usage information at runtime using a run recorder, wherein the class usage information comprises one or more of a miss rate of skeletons or contents, missed skeletons or contents and a non-usage rate of skeletons or contents, the missed skeletons or contents being recorded in a first-in first-out manner using a storage space with a fixed size; and

optimizing the class archive by removing a plurality of unused skeletons during runtime from the class contraction portion of the class archive, and adding a plurality of contents loaded during runtime to the class contraction portion of the class archive.

12. The method according to claim 11, further comprising:

separating each of the plurality of classes into a skeleton describing basic class information and contents describing detailed class information, and causing the class contraction portion to only include the skeleton of the class.

13. The method according to claim 11, wherein the organizing is carried out according to class usage information at runtime to cause the class contraction portion to only include a skeleton of a class to be used describing basic class information and contents to be used of the class describing detailed class information.

14. The method according to claim 11, wherein an original reorganizing of the class archive is carried out on the class archive to transform original class information in the class archive into a plurality of different class files.

15. The method according to claim 14, wherein contents describing detailed class information are separated into one or more class archives in accordance with the granularity required for loading.