Hybrid virtual thread context switching mechanism

A system for hybrid virtual thread context switching, the system comprising:

• a storage device that stores program instructions;
• one or more processors operably connected to the storage device and configured to execute the program instructions to cause the system to:
• responsive to preparation of scheduling a number of virtual threads to run on a virtual machine on a host system, determine whether a virtual thread requires a stack;
• responsive to a determination that the virtual thread requires a stack, determine whether low memory has enough space to allocate a stack;
• responsive to a determination that low memory has enough space, allocate a stack in low memory to the virtual thread;
• responsive to a determination that low memory does not have enough space, copy at least one unused stack from low memory to high memory;
• responsive to a determination that the virtual thread does not require a stack, determine whether a virtual thread stack is in low memory;
• responsive to a determination that the virtual thread stack is not in low memory, determine whether there is enough space in low memory to copy the virtual thread stack from high memory into low memory;
• responsive to a determination that there is enough space in low memory to copy the virtual thread stack from the high memory into low memory, copy the virtual thread stack from high memory to low memory;
• responsive to a determination that there is not enough space in low memory to copy the virtual thread stack from high memory into low memory, copy at least one unused stack from low memory to high memory;
• responsive to a determination that the virtual thread stack is in low memory, perform a stack switch for the virtual thread;
• and
• schedule the virtual thread on a carrier thread of the virtual machine.

A computer program product for hybrid virtual thread context switching, the computer program product comprising:

• a persistent storage medium having program instructions configured to cause one or more processors to:
• responsive to preparation of scheduling a number of virtual threads to run on a virtual machine on a host system, determine whether a virtual thread requires a stack;
• responsive to a determination that the virtual thread requires a stack, determine whether low memory has enough space to allocate a stack;
• responsive to a determination that low memory has enough space, allocate a stack in low memory to the virtual thread;
• responsive to a determination that low memory does not have enough space, copy at least one unused stack from low memory to high memory;
• responsive to a determination that the virtual thread does not require a stack, determine whether a virtual thread stack is in low memory;
• responsive to a determination that the virtual thread stack is not in low memory, determine whether there is enough space in low memory to copy the virtual thread stack from high memory into low memory;
• responsive to a determination that there is enough space in low memory to copy the virtual thread stack from the high memory into low memory, copy the virtual thread stack from high memory to low memory;
• responsive to a determination that there is not enough space in low memory to copy the virtual thread stack from high memory into low memory, copy at least one unused stack from low memory to high memory;
• responsive to a determination that the virtual thread stack is in low memory, perform a stack switch for the virtual thread;
• and
• schedule the virtual thread on a carrier thread of the virtual machine.