壓縮式快取記憶體通常被利用在末級快取記憶體上來增加有效的儲存空間 [1]。然而，因為各種資料壓縮的大小不同，導致在這種快取記憶體架構無法避免的儲存碎片問題。當儲存碎片問題發生時，通常會執行重整處理來挪出連續的儲存空間。這種重整處理會造成額外的時間週期負擔還有降低壓縮式快取記憶體架構的效率。在此，我們提出了一個免重整的壓縮式快取記憶體架構，可以完全減少執行重整處理所需要的時間。基於此架構，我們證明了我們的結果比傳統的快取記憶體架構增加了16%的系統性能並且減少了16%的能量消耗。我們的架構也比 Alameldeen 等人 [1]所提出的架構增加了5%的系統性能並且減少了3%的能量消耗。與 Sardashti等人 [2]所提出的架構，我們也多增進了3%的系統性能還有降低了2%的能量消耗。

Compressed cache was used in shared last level cache (LLC) to increase the effective capacity [1]. However, because of various data compression sizes, fragmentation problem of storage is inevitable in this cache design. When it happens, usually, a compaction process
is invoked to make contiguous storage space. This compaction process induces extra cycle penalty and degrades the effectiveness of compressed cache design. In this paper, we propose a compaction-free compressed cache architecture which can completely eliminate the time for executing compaction. Based on this cache design, we demonstrate that our results, compared with the conventional cache, have system performance improvement by 16% and energy reduction by 16% . Compared with the work by Alameldeen et al. [1], our design
has 5% more performance improvement and 3% more energy reduction. Compared with the work by Sardashti et al. [2], our design has 3% more performance improvement and 2% more
energy reduction.
i

1 Introduction 1
2 Previous Work 4
2.1 Data Compression Algorithms for Compressed Cache . . . . . . . . . . . . . 4
2.2 Compressed Cache Management . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3 Compressed LLC Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3 Background and Motivation 6
3.1 Review of Decoupled Variable-Segment Cache Architecture . . . . . . . . . . 6
3.2 Compaction Overhead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4 Methodology 12
4.1 Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2 Hardware Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5 Experimental Results 19
5.1 Experimental Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.2 Performance and Energy Results . . . . . . . . . . . . . . . . . . . . . . . . 20
5.3 Area Overhead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.4 Analysis of Performance and Area Overhead with Dierent Compression Seg-
ment Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
6 Conclusions 25

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