Method and System For Exception-Less System Calls In An Operating System

Abstract

A method and system is disclosed which can enhance the performance of computer systems by altering the operation of the operating system of those computer systems. The invention provides a system and method for making exception-less system calls, decoupling the invocation and execution of system calls, thus avoiding or reducing the direct and indirect overheads associated with making a conventional exception-based system call. The invention can be employed with single core processor systems and with multi-core processor systems, both affording improved temporal execution locality and the later also providing improved spatial execution locality. The system and method can be employed in a wide range of operating systems.

We claim: 
     
         1 . A non-transitory computer readable medium having instructions stored thereon for a system of performing exception-less system calls on a computer system executing an operating system having a user mode and a kernel mode, the operating system executing at least one user application, comprising:
 instructions for creating a shared memory space between the at least one user application executing in user mode and the operating system executing in kernel mode;   instructions for the user application to place a request for at least one system call into the shared memory space;   instructions for the operating system, in kernel mode, to check the shared memory space from time to time to identify system calls requested by the at least one user application;   instructions for the operating system to perform at least one identified system call for the at least one user application and to indicate completion of the at least one identified system call to the at least one user application via the shared memory space; and   instructions for the at least one user application to check the shared memory space from time to time to determine when the at least one system call has been completed.   
     
     
         2 . The non-transitory computer readable medium of  claim 1  further including instructions to have the operating system perform the at least one requested system call on a temporally scheduled basis. 
     
     
         3 . The non-transitory computer readable medium of  claim 1  wherein the computer system includes at least two processor cores and further including instructions to have the operating system select at least one of the at least two processor cores and to cause the system calls to be preferentially performed on the selected at least one processor core. 
     
     
         4 . The non-transitory computer readable medium of  claim 1  wherein the instructions for the operating system cause a system call thread executing in the kernel mode of the operating system to check the status of at least one system call entry in the shared memory space to identify the at least one requested exception-less system call waiting to be performed and to execute the system call requested by the identified at least one exception-less system call entry. 
     
     
         5 . A computer-implemented method of performing exception-less system calls on a computer system executing an operating system having a user mode and a kernel mode, the operating system executing at least one user application, the method comprising the steps of:
 creating a shared memory space between the user application and the operating system for each at least one user application;   in the shared memory space of each at least one user application, creating a system call entry for each of at least one exception-less system call;   instantiating a system call thread in the operating system kernel for each system call entry in each shared memory space;   allowing the at least one user application to set the contents of the at least one system call entry to request the performance of a system call by the operating system and to set the status of that system call entry appropriately;   causing a system call thread executing in the kernel space of the operating system to check the status of at least one system call entry in the shared memory space to identify a requested exception-less system call waiting to be performed and to execute the system call requested by that system call entry and to update the corresponding status of that system call entry; and   causing the at least one user application to check the status of the system call entries in the shared memory space to determine when a corresponding exception-less system call has been completed.