2,141 research outputs found
Improving Phase Change Memory Performance with Data Content Aware Access
A prominent characteristic of write operation in Phase-Change Memory (PCM) is
that its latency and energy are sensitive to the data to be written as well as
the content that is overwritten. We observe that overwriting unknown memory
content can incur significantly higher latency and energy compared to
overwriting known all-zeros or all-ones content. This is because all-zeros or
all-ones content is overwritten by programming the PCM cells only in one
direction, i.e., using either SET or RESET operations, not both. In this paper,
we propose data content aware PCM writes (DATACON), a new mechanism that
reduces the latency and energy of PCM writes by redirecting these requests to
overwrite memory locations containing all-zeros or all-ones. DATACON operates
in three steps. First, it estimates how much a PCM write access would benefit
from overwriting known content (e.g., all-zeros, or all-ones) by
comprehensively considering the number of set bits in the data to be written,
and the energy-latency trade-offs for SET and RESET operations in PCM. Second,
it translates the write address to a physical address within memory that
contains the best type of content to overwrite, and records this translation in
a table for future accesses. We exploit data access locality in workloads to
minimize the address translation overhead. Third, it re-initializes unused
memory locations with known all-zeros or all-ones content in a manner that does
not interfere with regular read and write accesses. DATACON overwrites unknown
content only when it is absolutely necessary to do so. We evaluate DATACON with
workloads from state-of-the-art machine learning applications, SPEC CPU2017,
and NAS Parallel Benchmarks. Results demonstrate that DATACON significantly
improves system performance and memory system energy consumption compared to
the best of performance-oriented state-of-the-art techniques.Comment: 18 pages, 21 figures, accepted at ACM SIGPLAN International Symposium
on Memory Management (ISMM
A Cache Management Strategy to Replace Wear Leveling Techniques for Embedded Flash Memory
Prices of NAND flash memories are falling drastically due to market growth
and fabrication process mastering while research efforts from a technological
point of view in terms of endurance and density are very active. NAND flash
memories are becoming the most important storage media in mobile computing and
tend to be less confined to this area. The major constraint of such a
technology is the limited number of possible erase operations per block which
tend to quickly provoke memory wear out. To cope with this issue,
state-of-the-art solutions implement wear leveling policies to level the wear
out of the memory and so increase its lifetime. These policies are integrated
into the Flash Translation Layer (FTL) and greatly contribute in decreasing the
write performance. In this paper, we propose to reduce the flash memory wear
out problem and improve its performance by absorbing the erase operations
throughout a dual cache system replacing FTL wear leveling and garbage
collection services. We justify this idea by proposing a first performance
evaluation of an exclusively cache based system for embedded flash memories.
Unlike wear leveling schemes, the proposed cache solution reduces the total
number of erase operations reported on the media by absorbing them in the cache
for workloads expressing a minimal global sequential rate.Comment: Ce papier a obtenu le "Best Paper Award" dans le "Computer System
track" nombre de page: 8; International Symposium on Performance Evaluation
of Computer & Telecommunication Systems, La Haye : Netherlands (2011
On using micro-clouds to deliver the fog
The cloud is scalable and cost-efficient, but it is not ideal for hosting all applications. Fog computing proposes an alternative of offloading some computation to the edge. Which applications to offload, where to, and when is not entirely clear yet due to our lack of understanding of potential edge infrastructures. Through a number of experiments, we showcase the feasibility and readiness of micro-clouds formed by collections of Raspberry Pis to host a range of fog applications, particularly for network-constrained environments
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