Enhancing lifetime and security of PCM-based Main Memory with Start-Gap Wear Leveling
Enhancing lifetime and security of PCM-based Main Memory with Start-Gap Wear Leveling
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DOI：
10.1145/1669112.1669117
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发表时间：
2009-12
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影响因子：
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通讯作者：
Moinuddin K. Qureshi;J. Karidis;M. Franceschini;Vijayalakshmi Srinivasan;L. Lastras;B. Abali
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文献类型：
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作者：
Moinuddin K. Qureshi;J. Karidis;M. Franceschini;Vijayalakshmi Srinivasan;L. Lastras;B. Abali
相变存储器（PCM）是一种新兴的存储器技术，其可以以成本效益和功率效率高的方式增加主存储器容量。然而，PCM单元最多只能承受107-108次写入，使得基于PCM的系统在理想条件下只有几年的寿命。此外，我们发现，在不同的单元写入的非均匀性减少了PCM系统的可实现的寿命的20倍。通过磨损均衡，可以使对PCM单元的写入保持一致。不幸的是，现有的损耗均衡技术需要大的存储表和间接，导致显著的面积和延迟开销。我们提出了启动间隙，一个简单的，新颖的，有效的磨损均衡技术，只使用两个寄存器。通过结合启动间隙与简单的地址空间随机化技术，我们表明，基线16 GB PCM为基础的系统的可实现的生命周期从5%（没有磨损均衡）提高到理论最大值的97%，同时产生的总存储开销小于13字节，避免了访问大型表的延迟开销。我们还分析了具有有限写入耐力的内存系统的安全漏洞，表明在对抗性设置下，基于PCM的系统可以在不到一分钟的时间内失败。我们提供了一个简单的扩展启动差距，使基于PCM的系统强大的恶意攻击。
Phase Change Memory (PCM) is an emerging memory technology that can increase main memory capacity in a cost-effective and power-efficient manner. However, PCM cells can endure only a maximum of 107-108 writes, making a PCM based system have a lifetime of only a few years under ideal conditions. Furthermore, we show that non-uniformity in writes to different cells reduces the achievable lifetime of PCM system by 20×. Writes to PCM cells can be made uniform with Wear-Leveling. Unfortunately, existing wear-leveling techniques require large storage tables and indirection, resulting in significant area and latency overheads. We propose Start-Gap, a simple, novel, and effective wear-leveling technique that uses only two registers. By combining Start-Gap with simple address-space randomization techniques we show that the achievable lifetime of the baseline 16 GB PCM-based system is boosted from 5% (with no wear-leveling) to 97% of the theoretical maximum, while incurring a total storage overhead of less than 13 bytes and obviating the latency overhead of accessing large tables. We also analyze the security vulnerabilities for memory systems that have limited write endurance, showing that under adversarial settings, a PCM-based system can fail in less than one minute. We provide a simple extension to Start-Gap that makes PCM-based systems robust to such malicious attacks.