Hardware and operating system support for persistent memory on a memory bus

1. A computing device comprising:

a central processing unit (CPU) component that enforces ordering and atomicity in a memory system of the computing device based in part by assigning an epoch identifier (epoch ID) to enforce writes;

a byte-addressable non-volatile memory component that is directly connected to a memory bus and directly accessed by the CPU component; and

a dynamic random access memory (DRAM), placed side by side with the byte-addressable non-volatile memory component.

2. The computing device of claim 1 , wherein the CPU component further includes a cache controller component and a memory controller component.

3. The computing device of claim 1 , wherein the CPU component provides ordering of writes to enforce correctness guarantees.

4. The computing device of claim 1 , wherein the byte-addressable non-volatile memory component is capable of using small and random writes to reduce traffic in the memory bus.

5. The computing device of claim 1 , wherein the byte-addressable non-volatile memory component is directly connected to the memory bus to obtain CPU speed.

6. The computing device of claim 1 , wherein the byte-addressable non-volatile memory component is a phase change memory (PCM).

7. The computing device of claim 1 , wherein the DRAM is used for stack and heap to improve wear lifetime of the byte-addressable non-volatile memory component.

8. The computing device of claim 1 , wherein the CPU component further comprises:

a cache controller component that uses the epoch ID, a persistence bit, and a dirty block counter to enforce ordering of writes; and

a memory controller component that enforces the ordering of writes by providing a timing restraint in addition to the persistence bit, the dirty block counter, and the epoch ID.

9. The computing device of claim 8 , wherein the memory controller component comprises:

a scheduler component that provides timing to the memory controller component; and

a memory controller transaction component that contains data to be flushed according to the timing provided by the scheduler component.

10. The computing device of claim 8 , wherein the persistence bit is used to reference the data that is to be written in the byte-addressable non-volatile memory component.

11. The computing device of claim 8 , wherein the memory controller component assures that a write cannot be reflected in the byte-addressable non-volatile memory component before in-flight writes associated with all earlier epochs are performed.

12. A computing device comprising:

a central processing unit (CPU) component, wherein the CPU component provides an epoch identifier (epoch ID);

a cache controller component coupled to the CPU component to enforce ordering and atomicity of writes to a memory system of the computing device based in part on the epoch identifier (epoch ID);

a memory controller component coupled to the CPU component to enforce the ordering and atomicity of the writes based in part on the epoch ID and in part on a timing restraint; and

a memory component directly accessible by the CPU component.

13. The computing device of claim 12 , wherein the memory component comprises:

a persistent memory component; and

a dynamic random access memory (DRAM).

14. The computing device of claim 13 , wherein the DRAM and the persistent memory component are directly coupled to a memory bus.

15. The computing device of claim 12 , wherein the memory controller component is integrated into the CPU component.

16. The computing device of claim 12 , wherein the memory controller component includes added state bits to track the epoch ID for the timing and scheduling of writes.

17. A computer system comprising:

a non-volatile memory component;

a dynamic random access memory (DRAM) coupled to the non-volatile memory component; and

a central processing unit (CPU) to enforce ordering and atomicity of writes to the non-volatile memory component, the CPU comprising a scheduler component and a memory controller transaction component to flush data according to timing provided by the scheduler component.

18. The computer system of claim 17 , wherein the scheduler component integrates access of the non-volatile memory component and the DRAM.

19. The computer system of claim 17 , wherein the CPU, the DRAM, and the non-volatile memory component are directly coupled to a memory bus.

20. The computer system of claim 17 , wherein the memory controller transaction component also uses persistence bits to represent the data.