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LightPC Presents a Resilient System Using Only Non-Volatile Memory 
View : 6549 Date : 2022-04-25 Writer : PR Office

Lightweight Persistence Centric System (LightPC) ensures both data
and execution persistence for energy-efficient full system
persistence

A KAIST research team has developed hardware and software technology
that ensures both data and execution persistence. The Lightweight
Persistence Centric System (LightPC) makes the systems resilient
against power failures by utilizing only non-volatile memory as the
main memory. 

"We mounted non-volatile memory on a system board prototype and
created an operating system to verify the effectiveness of LightPC,"
said Professor Myoungsoo Jung. The team confirmed that LightPC
validated its execution while powering up and down in the middle of
execution, showing up to eight times more memory, 4.3 times faster
application execution, and 73% lower power consumption compared to
traditional systems.

Professor Jung said that LightPC can be utilized in a variety of
fields such as data centers and high-performance computing to provide
large-capacity memory, high performance, low power consumption, and
service reliability.

In general, power failures on legacy systems can lead to the loss of
data stored in the DRAM-based main memory. Unlike volatile memory
such as DRAM, non-volatile memory can retain its data without power.
Although non-volatile memory has the characteristics of lower power
consumption and larger capacity than DRAM, non-volatile memory is
typically used for the task of secondary storage due to its lower
write performance. For this reason, nonvolatile memory is often used
with DRAM. However, modern systems employing non-volatile
memory-based main memory experience unexpected performance
degradation due to the complicated memory microarchitecture.

To enable both data and execution persistent in legacy systems, it is
necessary to transfer the data from the volatile memory to the
non-volatile memory. Checkpointing is one possible solution. It
periodically transfers the data in preparation for a sudden power
failure. While this technology is essential for ensuring high
mobility and reliability for users, checkpointing also has fatal
drawbacks. It takes additional time and power to move data and
requires a data recovery process as well as restarting the system.

In order to address these issues, the research team developed a
processor and memory controller to raise the performance of
non-volatile memory-only memory. LightPC matches the performance of
DRAM by minimizing the internal volatile memory components from
non-volatile memory, exposing the non-volatile memory (PRAM) media to
the host, and increasing parallelism to service on-the-fly requests
as soon as possible. 

The team also presented operating system technology that quickly
makes execution states of running processes persistent without the
need for a checkpointing process. The operating system prevents all
modifications to execution states and data by keeping all program
executions idle before transferring data in order to support
consistency within a period much shorter than the standard power
hold-up time of about 16 minutes. For consistency, when the power is
recovered, the computer almost immediately revives itself and
re-executes all the offline processes immediately without the need
for a boot process.

The researchers will present their work (LightPC: Hardware and
Software Co-Design for Energy-Efficient Full System Persistence) at
the International Symposium on Computer Architecture (ISCA) 2022 in
New York in June. More information is available at the CAMELab
website (http://camelab.org).

Figure 1. Customized system prototype (left: System prototype, Right:
Implementation view)

< Figure 1. Customized system prototype (left: System prototype,
Right: Implementation view) >

Figure 2. Overview of the proposed LightPC

< Figure 2. Overview of the proposed LightPC >

Figure 3. Energy and performance of the LightPC/LegacyPC (Right:
Cycle norm. to legacy PC)

< Figure 3. Energy and performance of the LightPC/LegacyPC (Right:
Cycle norm. to legacy PC) >

-Profile: 
Professor Myoungsoo Jung 
Computer Architecture and Memory Systems Laboratory (CAMEL)
http://camelab.org 
School of Electrical Engineering
KAIST



Non-Volatile Memoryvolatile memory checkpointing International
Symposium on Computer Architecture Professor Myoungsoo Jung College
of Engineering School of Electrical Engineering Computer Architecture
and Memory Systems Laboratory (CAMEL)
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