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The virtual-to-physical address translation overhead, a major performance bottleneck for modern workloads, can be effectively alleviated with huge pages. However, since huge pages must be mapped contiguously, OSs have not been able to use them well because of the memory fragmentation problem despite hardware support for huge pages being available for nearly two decades.This paper presents a comprehensive study of the interaction of fragmentation with huge pages in the Linux kernel. We observe that when huge pages are used, problems such as high CPU utilization and latency spikes occur because of unnecessary work (e.g., useless page migration) performed by memory management related subsystems due to the poor handling of unmovable (i.e., kernel) pages. This behavior is even more harmful in virtualized systems where unnecessary work may be performed in both guest and host OSs.We present Illuminator, an efficient memory manager that provides various subsystems, such as the page allocator, the ability to track all unmovable pages. It allows subsystems to make informed decisions and eliminate unnecessary work which in turn leads to cost-effective huge page allocations. Illuminator reduces the cost of compaction (up to 99%), improves application performance (up to 2.3×) and reduces the maximum latency of MySQL database server (by 30×).

Tensile properties, deformation, and fracture behavior of a wrought nickel-base superalloy 720Li have been studied in standard solutionized and two-stage-aged condition in the temperature range of 25°C to 750°C. Effect of strain rate on tensile behavior was assessed at 25°C, 400°C, and 750°C at five strain rates that range between 10 -5 s -1 and 10 -1 s -1 . The yield strength and ultimate tensile strength of the alloy remained unaffected by temperature until about 600°C and 500°C, respectively, typical of superalloys strengthened by fine and coherent intermetallic Ni 3 Al-based precipitates. The flow stress of the alloy was found to be insensitive to the strain rates studied at 25°C and 400°C. However, at 750°C, the flow stresses showed strain rate sensitivity at strain rates <10 -3 s -1 . The strain hardening behavior at 25°C and 400°C were similar. At 750°C, stain hardening was observed only at strain rates >10 -3 s -1 , and at lower strain rates, tensile instability was seen to set in immediately after yielding. The alloy exhibited ductile dimple fracture at all the temperatures and strain rates studied. Microstructural investigations indicate that in regimes where flow stresses are insensitive to strain rate, deformation occurs through heterogeneous planar slip, whereas in strain rate sensitive regimes, thermally activated diffusion processes promote homogeneous deformation.