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Efficient Process Checkpointing through Fine-Grained COW Management in New Memory based Systems
Jay H. Park, Young Je Moon, Sam H. Noh
We design and implement a process-based fault recovery system to increase the reliability of new memory based computer systems. A rollback point is made at every context switch to which a process can rollback to upon a fault. In this study, a clone process of the original process, which we refer to as a P-process (Persistent-process), is created as a rollback point. Such a design minimizes losses when a fault does occur. Specifically, first, execution loss can be minimized as rollback points are created only at context switches, which bounds the lost execution. Second, as we make use of the COW (Copy-On-Write）mechanism, only those parts of the process memory state that are modified (in page units) are copied decreasing the overhead for creating the P-process. Our experimental results show that the overhead is approximately 5% in 8 out of 11 PARSEC benchmark workloads when P-process is created at every context switch time. Even for workloads that result in considerable overhead, we show that this overhead can be reduced by increasing the P-process generation interval.
A Study of a Fast Booting Technique for a New memory+DRAM Hybrid Memory System
Hyeon Ho Song, Young Je Moon, Jae Hyeong Park, Sam H. Noh
Next generation memory technologies, which we denote as ‘new memory’, have both non-volatile and byte addressable properties. These characteristics are expected to bring changes to the conventional computer system structure. In this paper, we propose a fast boot technique for hybrid main memory architectures that have both new memory and DRAM. The key technique used for fast booting is write-tracking. Write-tracking is used to detect and manage modified data detection and involves setting the kernel region to read-only. This setting is used to trigger intentional faults upon modification requests. As the fault handler can detect the faulting address, write-tracking makes use of the address to manage the modified data. In particular, in our case, we make use of the MMU (Memory Management Unit) translation table. When a write occurs to the boot completed state, write-tracking preserves the original state of the modified address of the kernel region to a particular location, and execution continues. Upon booting, the fast booting process restores the preserved data to the original kernel region allowing rapid system boot-up. We develop the fast booting technique in an actual embedded board equipped with new memory. The boot time is reduced to less than half a second compared to around 15 seconds that is required for the original system.
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