Class sharing between multiple virtual machines

A computing system including first and second virtual machines and having a shared memory accessible to both said first and second virtual machines, the system further comprising:

• means for loading a class within the first virtual machine into said shared memory, said class having sharable and non-sharable data associated therewith;
• means for loading the class into the second virtual machine by locating the class within said shared memory;
• means for forming a mirror of the class within a private memory in the second virtual machine;
• and
• means for utilising the class in the second virtual machine on the basis of the sharable data from the shared memory of the first virtual machine, and the non-sharable data from the private memory of the second virtual machine;
• wherein said means for loading the class into the second virtual machine includes means for updating a class loader cache in the second virtual machine;
• and
• wherein said first and second virtual machines both include a hierarchy of class loaders, at least one of which is a shared class loader wherein each shared class loader in the class loader hierarchy in second virtual machine has a corresponding shared class loader in the equivalent position in the class loader hierarchy in the first virtual machine.

A computing system including:

• a first virtual machine;
• a second virtual machine;
• a shared memory accessible to both said first and second virtual machines;
• a private memory accessible to the second virtual machine;
• at least one class loaded in the first virtual machine into said shared memory, said class having sharable and non-sharable data associated therewith;
• a mirror of said at least one class loaded in the second virtual machine into said private memory, said mirror including the non-sharable data associated with the at least one class;
• wherein the at least one class is utilised by the second virtual machine on the basis of the sharable data from the shared memory of the first virtual machine, and the non-sharable data from the private memory of the second virtual machine
• wherein said second virtual machine loaded with said mirror of said at least one class includes an updated class loader cache in the second virtual machine;
• and
• wherein said first and second virtual machines both include a hierarchy of class loaders, at least one of which is a shared class loader, wherein each shared class loader in the class loader hierarchy in second virtual machine has a corresponding shared class loader in the equivalent position in the class loader hierarchy in the first virtual machine.

A computer program product comprising a computer readable medium including computer program instructions thereon which when executed by a computer system create first and second virtual machines, said computer system having a shared memory accessible to both said first and second virtual machines, the computer program instructions implementing a method comprising the steps of:

• loading a class within the first virtual machine into said shared memory, said class having sharable and non-sharable data associated therewith;
• loading the class into the second virtual machine by locating the class within said shared memory;
• forming a mirror of the class within a private memory in the second virtual machine;
• and
• utilising the class in the second virtual machine on the basis of the sharable data from the shared memory of the first virtual machine, and the non-sharable data from the private memory of the second virtual machine;
• wherein said step of loading the class into the second virtual machine includes updating a class loader cache in the second virtual machine;
• and
• wherein said first and second virtual machines both include a hierarchy of class loaders, at least one of which is a shared class loader, wherein each shared class loader in the class loader hierarchy in second virtual machine has a corresponding shared class loader in the equivalent position in the class loader hierarchy in the first virtual machine.