Reducing memory reference energy with opportunistic virtual caching
Reducing memory reference energy with opportunistic virtual caching
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通过机会虚拟缓存减少内存引用能量
DOI：
10.1145/2366231.2337194
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
M. Swift
中科院分区：
文献类型：
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作者：
Arkaprava Basu;M. Hill;M. Swift
大多数现代核心在每个内存访问中都表现出高度缔合的交易。这些设计通常通过与L1缓存访问重叠来隐藏TLB查找潜伏期，但是此重叠并没有隐藏TLB查找的功率。它甚至可以通过需要更高的关联L1缓存来加剧功率耗散。由于当今对耗电的关注，设计可以采用虚拟L1缓存，其中只有在L1缓存失误之后，TLB访问功率才能消散。不幸的是，虚拟缓存存在兼容性问题，例如支持可写的同义词和X86的物理页面助行器。这项工作提出了一个机会主义虚拟缓存（OVC），该虚拟缓存将虚拟缓存作为动态优化，通过允许某些内存块与虚拟地址和其他具有物理地址的其他内存块进行缓存。 OVC依赖于小型操作系统更改来发出信号，哪些页面可以使用虚拟缓存（例如，没有可写的同义词），但默认为物理缓存以兼容。我们通过分析表明了OVC的承诺，该分析发现存在虚拟缓存问题，但在动态上很少见。我们将Linux 2.6.28中的240行更改为启用OVC。在使用PARSEC和商业工作负载的实验中，所得系统可节省94-99％的TLB查找能量和近23％的L1 Cache动态查找能量。
Most modern cores perform a highly-associative transaction look aside buffer (TLB) lookup on every memory access. These designs often hide the TLB lookup latency by overlapping it with L1 cache access, but this overlap does not hide the power dissi-pated by TLB lookups. It can even exacerbate the power dissipation by requiring higher associativity L1 cache. With today's concern for power dissipation, designs could instead adopt a virtual L1 cache, wherein TLB access power is dissipated only after L1 cache misses. Unfortunately, virtual caches have compatibility issues, such as supporting writeable synonyms and x86's physical page table walker. This work proposes an Opportunistic Virtual Cache (OVC) that exposes virtual caching as a dynamic optimization by allowing some memory blocks to be cached with virtual addresses and others with physical addresses. OVC relies on small OS changes to signal which pages can use virtual caching (e.g., no writeable synonyms), but defaults to physical caching for compatibility. We show OVC's promise with analysis that finds virtual cache problems exist, but are dynamically rare. We change 240 lines in Linux 2.6.28 to enable OVC. On experiments with Parsec and commercial workloads, the resulting system saves 94-99% of TLB lookup energy and nearly 23% of L1 cache dynamic lookup energy.