Parallelizing Garbage Collection with I/O to Improve Flash Resource Utilization
- Authors
- Choi,Wonil; Jung,Myoungsoo; Kandemir,Mahmut; Das,Chita
- Issue Date
- Jun-2018
- Citation
- IEEE International Symposium on High Performance Distributed Computing, Proceedings, pp.243 - 254
- Indexed
- OTHER
- Journal Title
- IEEE International Symposium on High Performance Distributed Computing, Proceedings
- Start Page
- 243
- End Page
- 254
- URI
- https://scholarworks.bwise.kr/erica/handle/2021.sw.erica/113893
- DOI
- 10.1145/3208040.3208048
- ISSN
- 1082-8907
- Abstract
- Garbage Collection (GC) has been a critical optimization target for improving the performance of flash-based Solid State Drives (SSDs); the long-lasting GC process occupies the flash resources, thereby blocking normal I/O requests and increasing response times. This is a well-documented problem, and a wide range of prior works successfully hide the negative impact of GC on the I/O response times. In this paper, however, we unveil another serious side-effect of GC, called the plane under-utilization problem. More specifically, while a plane is busy doing GC, the other plane(s) in the same die remain idle, as all the planes in a die share a single command and address path that is dedicated to the GC. We also note that most of the
state-of-the-art proposals attacking the GC impact on I/O response times are not able to resolve the plane under-utilization problem, and in turn, miss a great potential to further improve the SSD performance. Thus, we next propose a scheduling technique, I/O-parallelized GC, which leverages the idle planes during GC to serve the blocked I/O requests. As a result, flash resources (planes) can be active during the most of GC time and the blocked I/O requests can get serviced quickly, and in turn, an improved SSD performance can be achieved. Using simulation-based evaluations over a wide variety of workloads, we show that the proposed I/O-parallelized GC scheme can improve the response times of the GC-affected I/O requests by
83% (reads) and 70% (writes), by increasing the average plane utilization from the (two planes-per-die) baseline 50% to 74.4% during GC. The I/O-parallelized GC is orthogonal to prior proposals that hide GC overheads; so, they can be combined for further SSD performance improvement.
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