Return to search

Efficient Memory Allocation for User and Library Variables in Recursive Programs with WCET/ACET Tunable Performance

Scratchpad Memory (SPM) is an alternative to cache. With SPM, the CPU¡¦s fast internal memory (ie, the SRAM) is directly mapped into the memory address space. This has the advantages of reduced power (by avoiding the memory management Unit, MMU, that a cache need to manage its tags and evictions), reduced area (for the same reason), and predictability.[1] Predictability is important in real-time systems, because each task must be assigned a deadline. If a task finishes early, there is no benefit. But if a task finishes late, then the effect is undesirable or even catastrophic. This means that the worst-case execution time (WCET) is more important than average-case execution time (ACET).
The disadvantage of SPM, when compared to cache, is that the SPM requires software management of the fast memory. In a previous student¡¦s work from our laboratory, [3], an SPM allocator was presented for WCET-targeted compilation.
Compared to that work, this current thesis make four key contributions. First, it introduces a significant amount of code infrastructure to allow library variables to be allocated to SPM. These variables turn out to represent a majority of all data accesses in many programs. Second, this provides support for allocating variables within recursive programs. Third, we support allocation of temporary variable (PC-relative addressing). Fourth, we have developed a simulator to obtain cycle-accurate information on memory behavior. In [3], the costs of allocation were not modeled, nor were the behaviors of the ARM¡¦s complex memory subsystem.
Keywords: SPM, memory allocation, memory modeling, library variables, WCET

Identiferoai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0209112-190129
Date09 February 2012
CreatorsFang, Hsin-Jan
ContributorsChung-Nan Lee, Steve W. Haga, CHUN-HUNG RICHARD LIN
PublisherNSYSU
Source SetsNSYSU Electronic Thesis and Dissertation Archive
LanguageEnglish
Detected LanguageEnglish
Typetext
Formatapplication/pdf
Sourcehttp://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0209112-190129
Rightsuser_define, Copyright information available at source archive

Page generated in 0.0022 seconds